Positive and method of producing the same and non-aqueous electrolyte battery

ABSTRACT

In a positive electrode of a non-aqueous electrolyte battery, at least one alkaline earth metal oxide selected from the group consisting of magnesium oxide, calcium oxide and barium oxide is dispersed between particles of an active substance for positive electrode, whereby a discharge capacity or recharge-discharge capacity of the non-aqueous electrolyte battery just after the preparation and after the storing at high temperature is improved.

TECHNICAL FIELD

This invention relates to a positive electrode for a non-aqueouselectrolyte battery and a method of producing the same as well as anon-aqueous electrolyte battery provided with such a positive electrode,and more particularly to positive electrodes for a non-aqueouselectrolyte primary battery and a non-aqueous electrolyte secondarybattery and a method of producing the same as well as a non-aqueouselectrolyte primary battery and a non-aqueous electrolyte secondarybattery provided with such a positive electrode.

BACKGROUND ART

Recently, batteries having a small size, a light weight, a long life anda high energy density are particularly demanded with the rapid advanceof electronics as a power source for small-size electronic equipments.In this connection, non-aqueous electrolyte primary batteries such as alithium primary battery using manganese dioxide as a positive electrodeand lithium as a negative electrode and the like are known as one ofbatteries having a high energy density because an electrode potential oflithium is lowest among metals and an electric capacity per unit volumeis large, and many kinds thereof are actively studies. On the otherhand, there are developed run-flat tires capable of continuously runningup to a repairing service place over a significant distance even ifpuncture or the like is caused in a pneumatic tire. Based on this, it isproposed to arrange on the run-flat tire an internal pressure alarmdevice which measures a tire internal pressure and transmits anaccident-informing signal when the internal pressure is dropped to notmore than a constant value. As a power source for the internal pressurealarm device is used the non-aqueous electrolyte primary battery havinga small size, a light weight, a long life and a high energy density andusing manganese dioxide as a positive electrode and lithium as anegative electrode.

In the above non-aqueous electrolyte primary battery, lithium isfrequently used as a material forming the negative electrode. However,since lithium violently reacts with a compound having an active protonsuch as water or alcohol, an electrolyte to be used is limited to anon-aqueous solution or a solid electrolyte. Since the solid electrolyteis low in the ion conductivity, it is limited only to the use at a lowdischarge current. Therefore, the electrolyte usually used at thepresent time is an aprotic organic solvent such as ester based organicsolvent or the like.

On the other hand, nickel-cadmium batteries were particularly the maincurrent as a secondary cell for backing up memories in AV-informationequipments such as personal computers, VTR and the like or a powersource for driving them. Recently, non-aqueous electrolyte secondarybatteries are considerably noticed instead of the nickel-cadmium batterybecause they are high in the voltage and have a high energy density anddevelop an excellent self-discharge characteristic, and hence variousdevelopments are attempted and a part thereof is commercialized. Forexample, a greater number of note-type personal computers, mobile phonesand so on are driven by such a non-aqueous electrolyte secondarybattery.

In the non-aqueous electrolyte secondary battery, sincelithium-containing composite oxide is used as a material forming apositive electrode and carbon is frequently used as a material forming anegative electrode, various organic solvents are used as an electrolytefor the purpose of reducing a risk when lithium is formed on the surfaceand rendering a driving voltage into a higher level. Also, an alkalimetal or the like (particularly, lithium metal or lithium alloy) is usedas a negative electrode in the non-aqueous electrolyte secondary batteryfor a camera, so that an aprotic organic solvent such as ester typeorganic solvent or the like is usually used as an electrolyte.

DISCLOSURE OF THE INVENTION

Although the non-aqueous electrolyte primary battery has a small size, alight weight, a long life and a high energy density as mentioned above,it is demanded to upgrade the function of the internal pressure alarmdevice so as to transmit various information of the tire in addition tothe tire internal pressure, and a power consumption is increasedaccompanied therewith, so that there are caused problems that theservice life becomes short and the exchange is required in a short timewhen the existing non-aqueous electrolyte primary batteries are used inthe power source for such an internal pressure alarm device. Also, sincethe temperature range of the tire used is wider, it is required tofurther improve the high-temperature characteristics of the batteryconsidering the use in desert and the like.

Furthermore, the material for the negative electrode in the non-aqueouselectrolyte primary battery is a lithium metal or a lithium alloy and isvery high in the activity to water, so that there is a problem that whenthe sealing of the battery is incomplete and water is penetrated intothe battery, the negative electrode material reacts with water toproduce hydrogen or cause ignition and hence the risk becomes high. Inaddition, since the lithium metal is low in the melting point (about170° C.), as a large current rapidly flows in the short-circuiting orthe like, there is a problem that the battery abnormally generates heatto cause a very risky state such as the fusion of the battery or thelike. Further, there is a problem that the electrolyte based on theorganic solvent is vaporized and decomposed accompanied with the aboveheat generation of the battery to produce a gas or theexplosion-ignition of the battery is caused by the produced gas or thelike. Moreover, even in the non-aqueous electrolyte primary battery notnaturally assuming the recharge, there is a problem that the rechargemay be carried out by wrong operation and in this case the ignition iscaused.

On the other hand, the existing non-aqueous electrolyte secondarybatteries are high in the energy density as compared with thenickel-cadmium battery, so that there is an advantage that therecharge-discharge capacity is high. However, in order to furthermitigate the burden of the user for recharging, it is required tofurther improve the recharge-discharge capacity. Also, since thetemperature range of the battery stored is wider, there is a problemthat the recharge-discharge capacity lowers when the battery isparticularly stored under a high-temperature environment.

Further, when an alkali metal (particularly lithium metal, lithium alloyor the like) is used as the negative electrode in the non-aqueouselectrolyte secondary battery, since the alkali metal is very high inthe activity to water content, there is a problem that if water ispenetrated into the battery due to incomplete sealing thereof or thelike, risks of generating hydrogen by reacting the negative electrodematerial with water, ignition and the like become high. Also, since thelithium metal is low in the melting point (about 170° C.), there is aproblem that if a large current violently flows in short-circuiting orthe like, there is caused a very risky state that the battery abnormallygenerates heat to cause the fusion of the battery or the like. Further,there is a problem that the electrolyte based on the above organicsolvent is vaporized or decomposed accompanied with the heat generationof the battery to generate a gas or the explosion-ignition of thebattery are caused by the generated gas.

It is, therefore, an object of the invention to provide a non-aqueouselectrolyte primary battery having a high discharge capacity anddeveloping an excellent discharge characteristic even after the storingat higher temperatures. Also, it is another object of the invention toprovide a non-aqueous electrolyte primary battery having a high safetyin addition to the high discharge capacity and the excellent dischargecharacteristic even after the storing at higher temperatures.

It is the other object of the invention to provide a non-aqueouselectrolyte secondary battery having a high recharge-discharge capacityand developing an excellent discharge characteristic even after thestoring at higher temperatures. Also, it is a further object of theinvention to provide a non-aqueous electrolyte secondary battery havinga high safety in addition to the high recharge-discharge capacity andthe excellent discharge characteristic even after the storing at highertemperatures.

As a result of various studies for achieving the above objects, theinventors have found that by improving a positive electrode in anon-aqueous electrolyte primary battery using manganese dioxide as anactive substance for the positive electrode is obtained a non-aqueouselectrolyte primary battery having a high discharge capacity just afterthe production and a high discharge capacity after the storing at a hightemperature, a high output and a long service life, and further byadding a phosphazene derivative and/or an isomer of a phosphazenederivative to an electrolyte is obtained a non-aqueous electrolyteprimary battery having higher discharge capacity just after theproduction and after the storing at the high temperature and a highsafety.

Also, the inventors have found that by improving a positive electrode ina non-aqueous electrolyte secondary battery using a lithium-containingcomposite oxide as an active substance for the positive electrode isobtained a non-aqueous electrolyte secondary battery having a highrecharge-discharge capacity just after the production and a highrecharge-discharge capacity after the storing at a high temperature, andfurther by adding a phosphazene derivative and/or an isomer of aphosphazene derivative to an electrolyte is obtained a non-aqueouselectrolyte secondary battery having higher recharge-discharge capacityjust after the production and after the storing at the high temperatureand a high safety.

That is, the invention is as follows:

-   1. A non-aqueous electrolyte primary battery characterized by    dispersing at least one alkaline earth metal oxide selected from the    group consisting of magnesium oxide, calcium oxide and barium oxide    between particles of manganese dioxide.-   2. A non-aqueous electrolyte primary battery according to the item    1, wherein the alkaline earth metal oxide is calcium oxide.-   3. A non-aqueous electrolyte primary battery according to the item 1    or 2, wherein a mass of the alkaline earth metal oxide is 0.5-4%    based on a mass of manganese dioxide.-   4. A non-aqueous electrolyte primary battery according to any one of    the items 1 to 3, wherein the alkaline earth metal oxide has a    particle size of 10-80 nm.-   5. A method of producing a positive electrode for a non-aqueous    electrolyte primary battery, which comprises the steps of:    -   (I) a step of adding an aqueous solution of at least one        alkaline earth metal hydroxide selected from the group        consisting of an aqueous solution of magnesium hydroxide, an        aqueous solution of calcium hydroxide and an aqueous solution of        barium hydroxide to manganese dioxide while cooling below 15° C.        and then mixing them with stirring to prepare a mixed solution;    -   (II) a step of raising a temperature of the mixed solution to        45-55° C. at a rate of 1-10° C./min to reduce a water content of        the mixed solution and further to 65-85° C. at a rate of 10-15°        C./min to remove the water content of the mixed solution to        thereby form a mixture of manganese dioxide and alkaline earth        metal hydroxide;    -   (III) a step of raising a temperature of the mixture to        290-310° C. and holding at this temperature for a given time to        convert the alkaline earth metal hydroxide into an alkaline        earth metal oxide to thereby prepare powder for a positive        electrode dispersing the alkaline earth metal oxide between        particles of manganese dioxide; and    -   (IV) a step of shaping the powder for a positive electrode to        produce a positive electrode.-   6. A method of producing a positive electrode for a non-aqueous    electrolyte primary battery according to the item 5, wherein the    aqueous solution of the alkaline earth metal hydroxide is an aqueous    solution of calcium hydroxide.-   7. A non-aqueous electrolyte primary battery comprising a positive    electrode as described in any one of the items 1 to 4, a negative    electrode, and an electrolyte comprising an aprotic organic solvent    and a support salt.-   8. A non-aqueous electrolyte primary battery according to the item    7, wherein the aprotic organic solvent is added with a phosphazene    derivative and/or an isomer of a phosphazene derivative.-   9. A non-aqueous electrolyte primary battery according to the item    8, wherein the phosphazene derivative has a viscosity at 25° C. of    not more than 300 mPa·s (300 cP) and is represented by the following    formula (I) or (II):-    (wherein R¹, R² and R³ are independently a monovalent substituent    or a halogen element, X¹ is a substituent containing at least one    element selected from the group consisting of carbon, silicon,    germanium, tin, nitrogen, phosphorus, arsenic, antimony, bismuth,    oxygen, sulfur, selenium, tellurium and polonium, and Y¹, Y² and Y³    are independently a bivalent connecting group, a bivalent element or    a single bond), or    (NPR⁴ ₂)_(n)  (II)-    (wherein R⁴ is a monovalent substituent or a halogen element, and n    is 3-15).-   10. A non-aqueous electrolyte primary battery according to the item    9, wherein the phosphazene derivative of the formula (II) is    represented by the following formula (III):    (NPF₂)_(n)  (III)-    (wherein n is 3-13).-   11. A non-aqueous electrolyte primary battery according to the item    9, wherein the phosphazene derivative of the formula (II) is    represented by the following formula (IV):    (NPR⁵ ₂)_(n)  (IV)-    (wherein R⁵ is a monovalent substituent or a halogen element, and    at least one of all R⁵s is a fluorine-containing monovalent    substituent or fluorine, provided that all R⁵s are not fluorine, and    n is 3-8).-   12. A non-aqueous electrolyte primary battery according to the item    8, wherein the phosphazene derivative is a solid at 25° C. and is    represented by the following formula (V):    (NPR⁶ ₂)_(n)  (V)-    (wherein R⁶ is a monovalent substituent or a halogen element, and n    is 3-6).-   13. A non-aqueous electrolyte primary battery according to the item    8, wherein the isomer of the phosphazene derivative is represented    by the following formula (VI) and is an isomer of a phosphazene    derivative represented by the following formula (VII):-    (in the formulae (VI) and (VII), R⁷, R⁸ and R⁹ are independently a    monovalent substituent or a halogen element, X² is a substituent    containing at least one element selected from the group consisting    of carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic,    antimony, bismuth, oxygen, sulfur, selenium, tellurium and polonium,    and Y⁷ and Y⁸ are independently a bivalent connecting group, a    bivalent element or a single bond).-   14. A non-aqueous electrolyte secondary battery characterized by    dispersing at least one alkaline earth metal oxide selected from the    group consisting of magnesium oxide, calcium oxide and barium oxide    between particles of at least one lithium-containing composite oxide    selected from the group consisting of LiCoO₂, LiNiO₂ and LiMn₂O₄.-   15. A non-aqueous electrolyte secondary battery according to the    item 14, wherein the alkaline earth metal oxide is calcium oxide.-   16. A non-aqueous electrolyte secondary battery according to the    item 14 or 15, wherein a mass of the alkaline earth metal oxide is    0.5-4% based on a mass of the lithium-containing composite oxide.-   17. A non-aqueous electrolyte secondary battery according to any one    of the items 14 to 16, wherein the alkaline earth metal oxide has a    particle size of 10-80 nm.-   18. A method of producing a positive electrode for a non-aqueous    electrolyte secondary battery, which comprises the steps of:    -   (I) a step of adding an aqueous solution of at least one        alkaline earth metal hydroxide selected from the group        consisting of an aqueous solution of magnesium hydroxide, an        aqueous solution of calcium hydroxide and an aqueous solution of        barium hydroxide to at least one lithium-containing composite        oxide selected from the group consisting of LiCoO₂, LiNiO₂ and        LiMn₂O₄ while cooling below 15° C. and then mixing them with        stirring to prepare a mixed solution;    -   (II) a step of raising a temperature of the mixed solution to        45-55° C. at a rate of 1-10° C./min to reduce a water content of        the mixed solution and further to 65-85° C. at a rate of 10-15°        C./min to remove the water content of the mixed solution to        thereby form a mixture of lithium-containing composite oxide and        alkaline earth metal hydroxide;    -   (III) a step of raising a temperature of the mixture to        290-310° C. and holding at this temperature for a given time to        convert the alkaline earth metal hydroxide into an alkaline        earth metal oxide to thereby prepare powder for a positive        electrode dispersing the alkaline earth metal oxide between        particles of the lithium-containing composite oxide; and    -   (IV) a step of shaping the powder for a positive electrode to        produce a positive electrode.-   19. A method of producing a positive electrode for a non-aqueous    electrolyte secondary battery according to the item 18, wherein the    aqueous solution of the alkaline earth metal hydroxide is an aqueous    solution of calcium hydroxide.-   20. A non-aqueous electrolyte secondary battery comprising a    positive electrode as described in any one of the items 14 to 17, a    negative electrode, and an electrolyte comprising an aprotic organic    solvent and a support salt.-   21. A non-aqueous electrolyte secondary battery according to the    item 20, wherein the aprotic organic solvent is added with a    phosphazene derivative and/or an isomer of a phosphazene derivative.-   22. A non-aqueous electrolyte secondary battery according to the    item 21, wherein the phosphazene derivative has a viscosity at    25° C. of not more than 300 mPa·s (300 cP) and is represented by the    following formula (I) or (II):-    (wherein R¹, R² and R³ are independently a monovalent substituent    or a halogen element, X¹ is a substituent containing at least one    element selected from the group consisting of carbon, silicon,    germanium, tin, nitrogen, phosphorus, arsenic, antimony, bismuth,    oxygen, sulfur, selenium, tellurium and polonium, and Y¹, Y² and Y³    are independently a bivalent connecting group, a bivalent element or    a single bond), or    (NPR⁴ ₂)_(n)  (II)-    (wherein R⁴ is a monovalent substituent or a halogen element, and n    is 3-15).-   23. A non-aqueous electrolyte secondary battery according to the    item 22, wherein the phosphazene derivative of the formula (II) is    represented by the following formula (III):    (NPF₂)_(n)  (III)-    (wherein n is 3-13).-   24. A non-aqueous electrolyte secondary battery according to the    item 22, wherein the phosphazene derivative of the formula (II) is    represented by the following formula (IV):    (NPR⁵ ₂)_(n)  (IV)-    (wherein R⁵ is a monovalent substituent or a halogen element, and    at least one of all R⁵s is a fluorine-containing monovalent    substituent or fluorine, provided that all R⁵s are not fluorine, and    n is 3-8).-   25. A non-aqueous electrolyte secondary battery according to the    item 21, wherein the phosphazene derivative is a solid at 25° C. and    is represented by the following formula (V):    (NPR⁶ ₂)_(n)  (V)-    (wherein R⁶ is a monovalent substituent or a halogen element, and n    is 3-6).-   26. A non-aqueous electrolyte secondary battery according to the    item 21, wherein the isomer of the phosphazene derivative is    represented by the following formula (VI) and is an isomer of a    phosphazene derivative represented by the following formula (VII):-    (in the formulae (VI) and (VII), R⁷, R⁸ and R⁹ are independently a    monovalent substituent or a halogen element, X² is a substituent    containing at least one element selected from the group consisting    of carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic,    antimony, bismuth, oxygen, sulfur, selenium, tellurium and polonium,    and Y⁷ and Y⁸ are independently a bivalent connecting group, a    bivalent element or a single bond).

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be described in detail below.

Positive Electrode for Non-Aqueous Electrolyte Primary Battery

The positive electrode for the non-aqueous electrolyte primary batteryaccording to the invention comprises manganese dioxide and an alkalineearth metal oxide dispersed between particles of manganese dioxide, andcontains additives usually used in the technical field of thenon-aqueous electrolyte primary battery such as an electricallyconductive agent, a binding agent and the like, if necessary.

Manganese dioxide used in the invention may be formed by either anelectrochemical synthesis or a chemical synthesis. Manganese dioxide ishigh in the discharge potential and the capacity, excellent in thesafety and wettability with an electrolyte and further excellent in thecost among materials usually used as an active substance for a positiveelectrode in the non-aqueous electrolyte primary battery. The particlesize of manganese dioxide is 1-60 μm, preferably 20-40 μm. When theparticle size is less than 1 μm or more than 60 μm, the packing isdeteriorated in the shaping of the positive electrode combined material(consisting of manganese dioxide, an electrically conductive agent and abinding agent) or the amount of the active substance for positiveelectrode included per unit volume (amount of manganese dioxide) becomesless, so that the discharge capacity may be undesirably reduced.

As the alkaline earth metal oxide used in the invention are mentionedmagnesium oxide (MgO), calcium oxide (CaO) and barium oxide (BaO), whichmay be used alone or in a combination of two or more. The alkaline earthmetal oxide is preferable to be very fine particles, which has aparticle size of 10-80 nm, preferably 10-60 nm. When the particle sizeis less than 10 nm, the synthesis of the particles is industriallydifficult, while when it exceeds 80 nm, the amount of manganese dioxideincluded as the active substance for positive electrode per unit volumedecreases and hence the energy quantity per unit volume unfavorablydecreases.

In the invention, the alkaline earth metal oxide is dispersed betweenthe particles of manganese dioxide, so that gaps are produced betweenthe particles of manganese dioxide. Since an electrolyte can efficientlypenetrate into these gaps, a contact area between the electrolyte andmanganese dioxide increases and hence the utilization ratio of manganesedioxide is increased and the discharge capacity and the energy densityare improved. Also, since the alkaline earth metal oxide is very high inthe water absorbability, a slight amount of water existing in thebattery can be removed, whereby reactions between manganese dioxide(positive electrode) and the electrolyte and between lithium (negativeelectrode) and the electrolyte at higher temperatures can be controlledand high-temperature characteristics of the non-aqueous electrolyteprimary battery can be considerably improved. Further, the alkalineearth metal oxide does not obstruct the battery electrode reaction ofthe non-aqueous electrolyte primary battery and does not cause thelowering of the electric conduction through addition (internalresistance does not rise). Among the above alkaline earth metal oxides,calcium oxide is preferable in view of the safety to environment.

In the positive electrode according to the invention, a mass of thealkaline earth metal oxide is preferable to be from 0.5% to 4% based ona mass of manganese dioxide. When the mass of the alkaline earth metaloxide is less than 0.5% based on the mass of manganese dioxide, theeffect of dispersing the alkaline earth metal oxide between theparticles of manganese dioxide to form gaps and the effect of removing aslight amount of water existing in the battery are not sufficient, whilewhen it exceeds 4%, the amount of manganese dioxide per unit volumedecreases and at the same time the surfaces of the particles ofmanganese dioxide are covered with the alkaline earth metal oxide tounfavorably lower the contact area between the electrolyte and manganesedioxide.

Among the additives added, if necessary, to the positive electrode forthe non-aqueous electrolyte primary battery according to the invention,the electrically conductive agent includes acetylene black and the like,and the binding agent includes polyvinylidene fluoride (PVDF),polytetrafluoroethylene (PTFE) and the like. These additives can be usedat the same compounding ratio as the conventional one, for example, acompounding ratio of powder for positive electrode (consisting ofmanganese dioxide and alkaline earth metal oxide):electricallyconductive agent:binding agent=8:1:1 to 8:1:0.2 (by mass).

The shape of the positive electrode is not particularly limited, and canbe properly selected from well-known shapes as an electrode. Forexample, there are mentioned sheet, cylinder, plate, spiral shape andthe like.

Production Method of Positive Electrode for Non-Aqueous ElectrolytePrimary Battery

In the positive electrode for the non-aqueous electrolyte primarybattery according to the invention, it is preferable to highly dispersevary fine particles of the alkaline earth metal oxide between theparticles of manganese dioxide, which can be prepared, for example, bythe following method. Moreover, the preparation method is notparticularly limited unless the very fine particles of the alkalineearth metal oxide can be highly dispersed between the particles ofmanganese dioxide.

The positive electrode for lithium primary battery according to theinvention can be produced according to the following first to fourthsteps. In the first step, an aqueous solution of at least one alkalineearth metal hydroxide selected from the group consisting of an aqueoussolution of magnesium hydroxide, an aqueous solution of calciumhydroxide and an aqueous solution of barium hydroxide is added tomanganese dioxide while cooling a reaction system below 15° C. and thenmixed with stirring to prepare a mixed solution. A method of coolingbelow 15° C. is not particularly limited, and can be attained, forexample, by water cooling. Moreover, the cooling is preferable to bebelow 4° C. from a viewpoint that the alkaline earth metal oxide ishighly dispersed between the particles of manganese dioxide, which canbe attained, for example, by ice cooling to not higher than 4° C. In theabove aqueous solution, a mass of the alkaline earth metal oxide ispreferable to be 3-5 g based on 100 g of water. The stirring is carriedout until manganese dioxide and the alkaline earth metal oxide aresufficiently uniformly dispersed into the aqueous solution.

In the second step, the mixed solution prepared in the first step israised to a temperature range of 45-55° C. at a rate of 1-10° C./min toreduce the water content of the mixed solution. Moreover, it ispreferable to reduce the water content to not more than 40% at thisstage. Subsequently, the mixed solution is raised to a temperature rangeof 65-75° C. at a rate of 10-15° C./min to remove the water content ofthe mixed solution and form a mixture of manganese dioxide and thealkaline earth metal hydroxide. Moreover, it is preferable to evaporate80-90% of the water content used at this stage. By rendering thetemperature rising rate into the above range to gradually evaporatewater can be highly dispersed the particles of the alkaline earth metalhydroxide at a fine particle state.

In the third step, the mixture obtained in the second step is raised toa temperature range of 290-310° C. and held at this temperature for agiven time to convert the alkaline earth metal hydroxide into analkaline earth metal oxide to thereby prepare powder for positiveelectrode dispersing the alkaline earth metal oxide between theparticles of manganese dioxide. Since almost all of water is removed atthe second step, the temperature rising rate is not particularly limitedat the third step. The time holding the alkaline earth metal oxide atthe above temperature is a time enough to convert the alkaline earthmetal hydroxide into the alkaline earth metal oxide by dehydration.Concretely, a time for converting not less than 98% of the alkalineearth metal hydroxide used into the alkaline earth metal oxide isproperly selected. For example, in case of the production scale thatmanganese dioxide used is about 10 g, power of an objective dehydrationratio is obtained by holding at the above temperature for 2-3 hours.After the completion of the dehydration, the temperature is dropped toroom temperature. It is preferable to gradually drop the temperature,which is preferably attained, for example, by air-cooling withoutblower.

Since calcium oxide is particularly preferable among the alkaline earthmetal oxides as mentioned above, an aqueous solution of calciumhydroxide is preferable as an aqueous solution of the alkaline earthmetal hydroxide used in the production method of the invention.

In the fourth step, a positive electrode for a non-aqueous electrolyteprimary battery is obtained by shaping the powder for positive electrodeobtained in the third step. The shaping method is not particularlylimited unless the positive electrode can be shaped so as to have astrength of the degree not breaking in the course of producing thenon-aqueous electrolyte primary battery, and there can be usedconventionally known methods. For instance, the powder for positiveelectrode can be punched out in a mold corresponding to the shape of thepositive electrode for an objective non-aqueous electrolyte primarybattery by means of a punching machine. Moreover, a paste is prepared bymixing and milling the powder for positive electrode with theaforementioned electrically conductive agent, binding agent and the likeand dried by hot air (100-120° C.) prior to the shaping, which mat bethen punched out by the punching machine.

The positive electrode obtained by the above method is at a state thatvery fine particles (particle size: 10-80 nm) of the alkaline earthmetal oxide are highly dispersed between the particles of manganesedioxide, and is a positive electrode for a non-aqueous electrolyteprimary battery having a considerably high discharge capacity, a highoutput and a long service life without largely decreasing the amount ofan active substance for positive electrode (amount of manganese dioxide)per unit volume as compared with the positive electrode consisting ofonly manganese dioxide. Also, the alkaline earth metal oxide is existentin the positive electrode, so that the positive electrode can absorb aslight amount of water existing in the battery, and even if the batteryusing such a positive electrode is placed under a high-temperatureenvironment, each electrode does not react with the electrolyte andhence the lowering of the discharge capacity is suppressed.

Positive Electrode for Non-Aqueous Electrolyte Secondary Battery

The positive electrode for the non-aqueous electrolyte secondary batteryaccording to the invention comprises a lithium-containing compositeoxide and an alkaline earth metal oxide dispersed between particles ofthe lithium-containing composite oxide, and contains additives usuallyused in the technical field of the non-aqueous electrolyte secondarybattery such as an electrically conductive agent, a binding agent andthe like, if necessary.

The lithium-containing composite oxide is a composite oxide of lithiumand a transition metal and is a substance directly contributing to anelectromotive reaction as an active substance for the non-aqueouselectrolyte secondary battery. As the lithium-containing composite oxideare mentioned LiCoO₂, LiNiO₂ and LiMn₂O₄. These lithium-containingcomposite oxides may be used alone or in a combination of two or more.The particle size of the lithium-containing composite oxide is 1-60 μm,preferably 20-40 μm. When the particle size is less than 1 μm or morethan 60 μm, the packing is deteriorated in the shaping of the positiveelectrode combined material (consisting of manganese dioxide, anelectrically conductive agent and a binding agent) or the amount of theactive substance for positive electrode included per unit volume becomesless, so that the recharge-discharge capacity may be undesirablyreduced.

As the alkaline earth metal oxide used in the invention are mentionedmagnesium oxide (MgO), calcium oxide (CaO) and barium oxide (BaO), whichmay be used alone or in a combination of two or more. The alkaline earthmetal oxide is preferable to be very fine particles, which has aparticle size of 10-80 nm, preferably 10-60 nm. When the particle sizeis less than 10 nm, the synthesis of the particles is industriallydifficult, while when it exceeds 80 nm, the amount of manganese dioxideincluded as the active substance for positive electrode per unit volumedecreases and hence the energy quantity per unit volume unfavorablydecreases.

In the invention, the alkaline earth metal oxide is dispersed betweenthe particles of the lithium-containing composite oxide, so that gapsare produced between the particles of the lithium-containing compositeoxide. Since an electrolyte can efficiently penetrate into these gaps, acontact area between the electrolyte and the lithium-containingcomposite oxide increases and hence the utilization ratio of thelithium-containing composite oxide is increased and therecharge-discharge is improved. Also, since the alkaline earth metaloxide is very high in the water absorbability, a slight amount of waterexisting in the battery can be removed, whereby reactions between thelithium-containing composite oxide and the electrolyte and betweenlithium and the electrolyte at higher temperatures can be controlled andhigh-temperature characteristics of the non-aqueous electrolytesecondary battery can be considerably improved. Further, the alkalineearth metal oxide does not obstruct the battery electrode reaction ofthe non-aqueous electrolyte secondary battery and does not cause thelowering of the electric conduction through addition (internalresistance does not rise). Among the above alkaline earth metal oxides,calcium oxide is preferable in view of the safety to environment.

In the positive electrode according to the invention, a mass of thealkaline earth metal oxide is preferable to be from 0.5% to 4% based ona mass of the lithium-containing composite oxide. When the mass of thealkaline earth metal oxide is less than 0.5% based on the mass of thelithium-containing composite oxide, the effect of dispersing thealkaline earth metal oxide between the particles of thelithium-containing composite oxide to form gaps and the effect ofremoving a slight amount of water existing in the battery are notsufficient, while when it exceeds 4%, the amount of the active substancefor positive electrode per unit volume decreases and at the same timethe surfaces of the particles of the lithium-containing composite oxideare covered with the alkaline earth metal oxide to unfavorably lower thecontact area between the electrolyte and the lithium-containingcomposite oxide.

Among the additives added, if necessary, to the positive electrode forthe non-aqueous electrolyte secondary battery according to theinvention, the electrically conductive agent includes acetylene blackand the like, and the binding agent includes polyvinylidene fluoride(PVDF), polytetrafluoroethylene (PTFE) and the like. These additives canbe used at the same compounding ratio as the conventional one, forexample, a compounding ratio of powder for positive electrode(consisting of lithium-containing composite oxide and alkaline earthmetal oxide):electrically conductive agent:binding agent=8:1:1 to8:1:0.2 (by mass).

The shape of the positive electrode is not particularly limited, and canbe properly selected from well-known shapes as an electrode. Forexample, there are mentioned sheet, cylinder, plate, spiral shape andthe like.

Production Method of Non-Aqueous Electrolyte Secondary Battery

In the positive electrode for the non-aqueous electrolyte secondarybattery according to the invention, it is preferable to highly dispersevary fine particles of the alkaline earth metal oxide between theparticles of lithium-containing composite oxide, which can be prepared,for example, by the following method. Moreover, the preparation methodis not particularly limited unless the very fine particles of thealkaline earth metal oxide can be highly dispersed between the particlesof the lithium-containing composite oxide.

The positive electrode for the non-aqueous electrolyte secondary batteryaccording to the invention can be produced according to the followingfirst to fourth steps. In the first step, an aqueous solution of atleast one alkaline earth metal hydroxide selected from the groupconsisting of an aqueous solution of magnesium hydroxide, an aqueoussolution of calcium hydroxide and an aqueous solution of bariumhydroxide is added to at least one lithium-containing composite oxideselected from the group consisting of LiCoO₂, LiNiO₂ and LiMn₂O₄ whilecooling a reaction system below 15° C. and then mixed with stirring toprepare a mixed solution. A method of cooling below 15° C. is notparticularly limited, and can be attained, for example, by watercooling. Moreover, the cooling is preferable to be below 4° C. from aviewpoint that the alkaline earth metal oxide is highly dispersedbetween the particles of the lithium-containing composite oxide, whichcan be attained, for example, by ice cooling to not higher than 4° C. Inthe above aqueous solution, a mass of the alkaline earth metal oxide ispreferable to be 3-5 g based on 100 g of water. The stirring is carriedout until the lithium-containing composite oxide and the alkaline earthmetal oxide are sufficiently uniformly dispersed into the aqueoussolution.

In the second step, the mixed solution prepared in the first step israised to a temperature range of 45-55° C. at a rate of 1-10° C./min toreduce the water content of the mixed solution. Moreover, it ispreferable to reduce the water content to not more than 40% at thisstage. Subsequently, the mixed solution is raised to a temperature rangeof 65-75° C. at a rate of 10-15° C./min to remove the water content ofthe mixed solution and form a mixture of the lithium-containingcomposite oxide and the alkaline earth metal hydroxide. Moreover, it ispreferable to evaporate 80-90% of the water content used at this stage.By rendering the temperature rising rate into the above range togradually evaporate water can be highly dispersed the particles of thealkaline earth metal hydroxide at a fine particle state.

In the third step, the mixture obtained in the second step is raised toa temperature range of 290-310° C. and held at this temperature for agiven time to convert the alkaline earth metal hydroxide into analkaline earth metal oxide to thereby prepare powder for positiveelectrode dispersing the alkaline earth metal oxide between theparticles of the lithium-containing composite oxide. Since almost all ofwater is removed at the second step, the temperature rising rate is notparticularly limited at the third step. The time holding the alkalineearth metal oxide at the above temperature is a time enough to convertthe alkaline earth metal hydroxide into the alkaline earth metal oxideby dehydration. Concretely, a time for converting not less than 98% ofthe alkaline earth metal hydroxide used into the alkaline earth metaloxide is properly selected. For example, in case of the production scalethat the lithium-containing composite oxide used is about 10 g, power ofan objective dehydration ratio is obtained by holding at the abovetemperature for 2-3 hours. After the completion of the dehydration, thetemperature is dropped to room temperature. It is preferable togradually drop the temperature, which is preferably attained, forexample, by air-cooling without blower.

Since calcium oxide is particularly preferable among the alkaline earthmetal oxides as mentioned above, an aqueous solution of calciumhydroxide is preferable as an aqueous solution of the alkaline earthmetal hydroxide used in the production method of the invention.

In the fourth step, a positive electrode for a non-aqueous electrolytesecondary battery is obtained by shaping the powder for positiveelectrode obtained in the third step. The shaping method is notparticularly limited unless the positive electrode can be shaped so asto have a strength of the degree not breaking in the course of producingthe non-aqueous electrolyte secondary battery, and there can be usedconventionally known methods. For instance, the powder for positiveelectrode is mixed and milled with the additives such as theaforementioned electrically conductive agent, binding agent and the likeand an organic solvent such as ethyl acetate, ethanol or the like, whichmay be subjected to a rolling through rollers to prepare a sheet havingdesired thickness and width.

The positive electrode obtained by the above method is at a state thatvery fine particles (particle size: 10-80 nm) of the alkaline earthmetal oxide are highly dispersed between the particles of thelithium-containing composite oxide, and is a positive electrode for anon-aqueous electrolyte secondary battery having a considerably highrecharge-discharge capacity, a high output and a long service lifewithout largely decreasing the amount of an active substance forpositive electrode (amount of lithium-containing composite oxide) perunit volume as compared with the positive electrode consisting of onlythe lithium-containing composite oxide. Also, the alkaline earth metaloxide is existent in the positive electrode, so that the positiveelectrode can absorb a slight amount of water existing in the battery,and even if the battery using such a positive electrode is placed undera high-temperature environment, each electrode does not react with theelectrolyte and hence the lowering of the discharge capacity issuppressed.

Non-Aqueous Electrolyte Battery

The non-aqueous electrolyte battery according to the invention comprisesthe aforementioned positive electrode, a negative electrode and anelectrolyte comprising an aprotic organic solvent and a support salt,and is provided with members usually used in the technical field of thenon-aqueous electrolyte battery such as a separator and the like, ifnecessary.

Negative Electrode

The material for the negative electrode in the non-aqueous electrolytebattery according to the invention partly differs between the primarybattery and the secondary battery. For example, as a negative electrodefor the non-aqueous electrolyte primary battery are mentioned lithiummetal, lithium alloy and the like. As a metal alloying with lithium arementioned Sn, Pb, Al, Au, Pt, In, Zn, Cd, Ag, Mn and the like. Amongthem, Al, Zn and Mg are preferable from a viewpoint of amount of depositand toxicity. These materials may be used alone or in a combination oftwo or more.

As a negative electrode for the non-aqueous electrolyte secondarybattery are preferably mentioned lithium metal, alloy of lithium withAl, In, Pb, Zn or the like, a carbon material such as graphite dopedwith lithium or the like, and so on. Among them, the carbon materialsuch as graphite or the like is preferable in view of a higher safety.These materials may be used alone or in a combination of two or more.

The shape of the negative electrode is not particularly limited, and maybe properly selected from the same known shapes as described on theshape of the positive electrode.

Non-Aqueous Electrolyte

The electrolyte in the non-aqueous electrolyte battery according to theinvention comprises an aprotic organic solvent and a support salt. Sincethe negative electrode for the non-aqueous electrolyte battery containsan alkali metal such as lithium or the like as mentioned above, it isvery high in the reactivity with water, so that the aprotic organicsolvent not reacting with water is used as a solvent. The aproticorganic solvent is made possible to lower the viscosity of theelectrolyte and can easily attain an optimum ion conduction as abattery.

Aprotic Organic Solvent

The aprotic organic solvent constituting the electrolyte for thenon-aqueous electrolyte battery of the invention is not particularlylimited, and includes ether compounds, ester compounds and the like froma viewpoint that the viscosity of the electrolyte is controlled to a lowvalue. Concretely, there are preferably mentioned 1,2-dimethoxyethane(DME), tetrahydrofuran, dimethyl carbonate, diethyl carbonate (DEC),diphenyl carbonate, ethylene carbonate (EC), propylene carbonate (PC),γ-butyrolactone (GBL), γ-valerolactone, methylethyl carbonate,ethylmethyl carbonate and the like.

Among them, a cyclic ester compound such as propylene carbonate,γ-butyrolactone or the like, a chain ester compound such as dimethylcarbonate, methylethyl carbonate or the like, a chain ether compoundsuch as 1,2-dimethoxyethane or the like are preferable in case of usingin the non-aqueous electrolyte primary battery, and a cyclic estercompound such as ethylene carbonate, propylene carbonate,γ-butyrolactone or the like, a chain ester compound such as dimethylcarbonate, ethylmethyl carbonate, diethyl carbonate or the like, a chainether compound such as 1,2-dimethoxyethane or the like are preferable incase of using in the non-aqueous electrolyte secondary battery. Thecyclic ester compound is high in the dielectric constant and excellentin the solubility of the above support salt, while the chain ester andether compounds are low in the viscosity and preferably lower theviscosity of the electrolyte. They may be used alone or in a combinationof two or more. The viscosity at 25° C. of the aprotic organic solventis not particularly limited, but is preferably not more than 3.0 mPa·s(3.0 cP), more preferably not more than 2.0 mPa·s (2.0 cP).

Support Salt

As the support salt, a support salt or the like forming an ionic sourcefor lithium ion is preferable. The ionic source for lithium ion is notparticularly limited, but there are preferably mentioned lithium saltssuch as LiClO₄, LiBF₄, LiPF₆, LiCF₃SO₃, LiAsF₆, LiC₄F₉SO₃, Li(CF₃SO₂)₂N,Li(C₂F₅SO₂)₂N and the like. They may be used alone or in a combinationof two or more.

The content of the support salt in the electrolyte is preferably 0.2-1mol, more preferably 0.5-1 mol per 1 kg of the solvent component in caseof the primary battery, and is preferably 0.2-1 mol, more preferably0.5-1 mol per 1 kg of the solvent component in case of the secondarybattery, When the content is less than 0.2 mol, the sufficient electricconduction of the electrolyte can not be ensured, and troubles may becaused in the discharge characteristic of the battery in case of theprimary battery and in the recharge-discharge characteristic of thebattery in case of the secondary battery, while when it exceeds 1 mol,the viscosity of the electrolyte increases and the sufficient mobilityof lithium ion can not be ensured and hence the sufficient electricconduction of the electrolyte can not be ensured likewise the above toraise solution resistance, and troubles may be caused in the pulsedischarge and low-temperature characteristic in case of the primarybattery and in the recharge-discharge characteristic in case of thesecondary battery.

Phosphazene Derivative and/or Isomer of Phosphazene Derivative

It is preferable to add a phosphazene derivative and/or an isomer of aphosphazene derivative to the aprotic organic solvent.

In the non-aqueous electrolyte primary battery, by dispersing the alkaliearth metal oxide into the particles of manganese dioxide as previouslymentioned, the discharge capacities just after the production of thenon-aqueous electrolyte primary battery and after the storing at thehigh temperature can be improved. Further, by adding the phosphazenederivative and/or the isomer of the phosphazene derivative to theaprotic organic solvent, the discharge capacities just after theproduction and after the storing at the high temperature can be moreimproved to obtain a non-aqueous electrolyte primary battery having ahigher output and a longer service life.

In the conventional electrolyte of the non-aqueous electrolyte primarybattery based on the aprotic organic solvent, when a large currentrapidly flows in the short-circuiting to abnormally generate heat in thebattery, it is high in the risk that the electrolyte is vaporized anddecomposed to produce a gas and the explosion-ignition of the battery iscaused by the produced gas and heat and also it is high in the risk thatthe battery is ignited by sparks produced in the short-circuiting tocause the explosion-ignition. If the phosphazene derivative and/or theisomer of the phosphazene derivative is included in the conventionalelectrolyte, the vaporization-decomposition of the electrolyte at arelatively low temperature of not higher than about 200° C. issuppressed to reduce the risk of the explosion-ignition, and even if theignition is caused in the interior of the battery by the fusion of thenegative electrode material or the like, the risk of catching fire islow. Further, phosphorus has an action of controlling chaindecomposition of high molecular weight material constituting thebattery, so that the risk of firing-ignition is effectively reduced. Inaddition, if the phosphazene derivative and/or the isomer of thephosphazene derivative is included in the conventional electrolyte, itis possible to provide a non-aqueous electrolyte primary battery havingexcellent low-temperature and high-temperature characteristics.Furthermore, the phosphazene derivative and the isomer of thephosphazene derivative have a potential window sufficient to function asa primary battery and do not decompose through discharging. Moreover,the phosphazene derivative containing a halogen (e.g. fluorine) and theisomer of such a phosphazene derivative function as an active radicalcatching agent if unexpected burning occurs, while the phosphazenederivative having an organic substituent and the isomer of such aphosphazene derivative produce carbide (char) on the electrode materialand the separator in the burning and have an effect of shutting offoxygen. In addition, if the recharging is accidentally carried out bythe user, since the phosphazene derivative and the isomer of thephosphazene derivative have an effect of controlling the formation ofdendrite, the safety becomes higher as compared with the systemcontaining no phosphazene derivative.

On the other hand, in the non-aqueous electrolyte secondary battery, bydispersing the alkali earth metal oxide into the particles of thelithium-containing composite oxide as previously mentioned, therecharge-discharge capacities just after the production of thenon-aqueous electrolyte secondary battery and after the storing at thehigh temperature can be improved. Further, by adding the phosphazenederivative and/or the isomer of the phosphazene derivative to theaprotic organic solvent, the recharge-discharge capacities just afterthe production and after the storing at the high temperature can be moreimproved.

In the conventional electrolyte of the non-aqueous electrolyte secondarybattery based on the aprotic organic solvent, when a large currentrapidly flows in the short-circuiting to abnormally generate heat in thebattery, it is high in the risk that the electrolyte is vaporized anddecomposed to produce a gas and the explosion-ignition of the battery iscaused by the produced gas and heat, so that the risk becomes high. Ifthe phosphazene derivative and/or the isomer of the phosphazenederivative is included in the conventional electrolyte, thevaporization-decomposition of the electrolyte at a relatively lowtemperature of not higher than about 200° C. is suppressed to reduce therisk of the explosion-ignition. Even if the ignition is caused in theinterior of the battery by the fusion of the negative electrode materialor the like, the risk of catching fire is low. Further, phosphorus hasan action of controlling chain decomposition of high molecular weightmaterial constituting the battery, so that the risk of fire-ignition iseffectively reduced, and it is possible to provide a non-aqueouselectrolyte secondary battery possessing excellent batterycharacteristics such as a high voltage, a high discharge capacity, alarge current dischargeability and the like. furthermore, if thephosphazene derivative and/or the isomer of the phosphazene derivativeis included in the conventional electrolyte, it is possible to provide anon-aqueous electrolyte primary battery having excellent low-temperatureand high-temperature characteristics. Moreover, the phosphazenederivative containing a halogen (e.g. fluorine) and the isomer of such aphosphazene derivative function as an active radical catching agent ifunexpected burning occurs, while the phosphazene derivative having anorganic substituent and the isomer of such a phosphazene derivativeproduce carbide (char) on the electrode material and the separator inthe burning and have an effect of shutting off oxygen. Even in therecharging, since the phosphazene derivative and the isomer of thephosphazene derivative have an effect of controlling the formation ofdendrite, the safety becomes higher as compared with the systemcontaining no phosphazene derivative.

In the invention, the risk of fire-ignition is evaluated by measuring anoxygen index according to JIS K7201. Moreover, the term “oxygen index”used herein means a value of a minimum oxygen concentration requiredwhen the burning of the material is maintained under given testconditions defined in JIS K7201 and represented by a volume percentage,in which the lower the oxygen index value, the higher the risk offire-ignition, and the higher the oxygen index value, the lower the riskof firing-ignition. In the invention, the risk of fire-ignition isevaluated by a limit oxygen index according to the above oxygen index.

It is preferable that the electrolyte added with the phosphazenederivative and/or the isomer of the phosphazene derivative has a limitoxygen index of not less than 21% by volume. When the limit oxygen indexis less than 21% by volume, the effect of controlling the fire-ignitionmay be insufficient. Since the oxygen index under atmospheric conditionis 20.2% by volume, the limit oxygen index of 20.2% by volume means thatcombustion occurs in atmosphere. The inventors have made various studiesand found that the self-extinguishing property is developed at the limitoxygen index of not less than 21% by volume, and the flame retardance isdeveloped at not less than 23% by volume, and the incombustibility isdeveloped at not less than 25% by volume.

Moreover, the terms “self-extinguishing property, flame retardance,incombustibility” used herein are defined in the method according to UL94HB method, wherein when a test piece of 127 mm×12.7 mm is prepared byimpregnating 1.0 mL of an electrolyte into an incombustible quartz fiberand is ignited under atmospheric environment, the self-extinguishingproperty indicates a case that the ignited flame is extinguished in aline between 25 mm and 100 mm and an object fallen down from a net isnot fired, and the flame retardance indicates a case that the ignitedflame does not arrive at a line of 25 mm of the apparatus and the objectfallen down from the net is not fired, and the incombustibilityindicates a case that no ignition is observed (combustion length: 0 mm).

The phosphazene derivative added to the aprotic organic solvent is notparticularly limited. However, from a viewpoint that the viscosity isrelatively low and the support salt is well dissolved, a phosphazenederivative having a viscosity at 25° C. of not more than 300 mPa·s (300cP) and represented by the following formula (I) or (II) is preferable.

(wherein R¹, R² and R³ are independently a monovalent substituent or ahalogen element, X¹ is a substituent containing at least one elementselected from the group consisting of carbon, silicon, germanium, tin,nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur,selenium, tellurium and polonium, and Y¹, Y² and Y³ are independently abivalent connecting group, a bivalent element or a single bond), or(NPR⁴ ₂)_(n)  (II)(wherein R⁴ is a monovalent substituent or a halogen element, and n is3-15).

The viscosity at 25° C. of the phosphazene derivative of the formula (I)or (II) is required to be not more than 300 mPa·s (300 cP), preferablynot more than 100 mPa·s (100 cP), further preferably not more than 20mPa·s (20 cP), particularly not more than 5 mPa·s (5 cP). When theviscosity exceeds 300 mPa·s (300 cP), the support saly is hardlydissolved, and the wettability onto the separator or the like lowers,and the ion electric conductivity is considerably decreased by theincrease of viscous resistance of the electrolyte, and particularlyperformances are lacking in the use under low-temperature conditionssuch as not higher than freezing point and the like. Also, thesephosphazene derivatives are liquid and have an electric conductivityequal to that of the usually liquid electrolyte and indicate excellentcycle characteristic in case of using in the electrolyte for thesecondary battery.

In the formula (I), R¹, R² and R³ are not particularly limited unlessthey are a monovalent substituent or a halogen element. As themonovalent substituent are mentioned an alkoxy group, an alkyl group, acarboxyl group, an acyl group, an aryl group and the like. Among them,the alkoxy group is preferable in a point that the viscosity of theelectrolyte can be made low. As the halogen element are preferablyfluorine, chlorine, bromine and the like. All of R¹-R³ may be the samekind of the substituent, or some of them may be different kinds of thesubstituents.

As the alkoxy group are mentioned, for example, methoxy group, ethoxygroup, propoxy group, butoxy group, and an alkoxy-substituted alkoxygroup such as methoxyethoxy group, methoxyethoxyethoxy group or thelike. Among them, all of R¹-R³ are preferable to be methoxy group,ethoxy group, methoxyethoxy group or methoxyethoxyethoxy group, and areparticularly preferable to be methoxy group or ethoxy group from aviewpoint of low viscosity and high dielectric constant. As the alkylgroup are mentioned methyl group, ethyl group, propyl group, butylgroup, pentyl group and the like. As the acyl group are mentioned formylgroup, acetyl group, propionyl group, butyryl group, isobutyryl group,valeryl group and the like. As the aryl group are mentioned phenylgroup, tolyl group, naphthyl group and the like. In these monovalentsubstituents, hydrogen element is preferable to be substituted with ahalogen element. As such a halogen element, fluorine, chlorine andbromine are preferable, and fluorine is particularly preferable, andchlorine is next preferable. In the secondary battery, when fluorine isused, there is a tendency that the cycle characteristics are good ascompared with chlorine.

In the formula (I), as the bivalent connecting group shown by Y¹, Y² andY³ are mentioned, for example, CH₂ group, and a bivalent connectinggroup containing at least one element selected from the group consistingof oxygen, sulfur, selenium, nitrogen, boron, aluminum, scandium,gallium, yttrium, indium, lanthanum, thallium, carbon, silicon,titanium, tin, germanium, zirconium, lead, phosphorus, vanadium,arsenic, niobium, antimony, tantalum, bismuth, chromium, molybdenum,tellurium, polonium, tungsten, iron, cobalt and nickel. Among them, CH₂group and the bivalent group containing at least one element selectedfrom the group consisting of oxygen, sulfur, selenium and nitrogen arepreferable, and the bivalent connecting group containing sulfur and/orselenium is particularly preferable. Also, Y¹, Y² and Y³ may be abivalent element such as oxygen, sulfur, selenium or the like, or asingle bond. All of Y¹-Y³ may be the same kind, or some of them may bedifferent kinds.

In the formula (I), X¹ is preferable to be a substituent containing atleast one element selected from the group consisting of carbon, silicon,nitrogen, phosphorus, oxygen and sulfur from a viewpoint of theconsideration on toxicity, environment and the like. Among thesesubstituents, a substituent represented by the following formula (VIII),(IX) or (X) is more preferable.

In the formulae (VIII), (IX) and (X), R¹⁰-R¹⁴ are independently amonovalent substituent or a halogen element, Y¹⁰-Y¹⁴ are independently abivalent connecting group, a bivalent element or a single bond, and Z¹is a bivalent group or a bivalent element.

As R¹⁰-R¹⁴ in the formulae (VIII), (IX) and (X) are preferably mentionedthe same monovalent substituents or halogen elements as described inR¹-R³ of the formula (I). They may be the same kind in the samesubstituent, or some of them may be different kinds. Also, R¹⁰ and R¹¹in the formula (VIII), and R¹³ and R¹⁴ in the formula (X) may be bondedto each other to form a ring.

As the group shown by Y¹⁰-Y¹⁴ in the formulae (VIII), (IX) and (X) arementioned the same bivalent connecting groups, bivalent elements and thelike as described in Y¹-Y³ of the formula (I). Similarly, the groupcontaining sulfur and/or selenium is particularly preferable because therisk of fire-ignition of the electrolyte is reduced. They may be thesame kind in the same substituent, or some of them may be differentkinds.

As Z¹ in the formula (VIII) are mentioned, for example, CH₂ group, CHRgroup (R is an alkyl group, an alkoxyl group, phenyl group or the like,and so forth), NR group, a bivalent group containing at least oneelement selected from the group consisting of oxygen, sulfur, selenium,nitrogen, boron, aluminum, scandium, gallium, yttrium, indium,lanthanum, thallium, carbon, silicon, titanium, tin, germanium,zirconium, lead, phosphorus, vanadium, arsenic, niobium, antimony,tantalum, bismuth, chromium, molybdenum, tellurium, polonium, tungsten,iron, cobalt and nickel, and the like. Among them, CH₂ group, CHR group.NR group and the bivalent group containing at least one element selectedfrom the group consisting of oxygen, sulfur and selenium is preferable.Particularly, the bivalent group containing sulfur and/or selenium ispreferable because the risk of fire-ignition of the electrolyte isreduced. Also, Z¹ may be a bivalent element such as oxygen, sulfur,selenium or the like.

Among these substituents, the substituent containing phosphorus asrepresented by the formula (VIII) is particularly preferable in a pointthat the risk of fire-ignition can be effectively reduced. Also, thesubstituent containing sulfur as represented by the formula (IX) isparticularly preferable in a point that the interfacial resistance ofthe electrolyte can be made small.

In the formula (II), R⁴ is not particularly limited unless it is amonovalent substituent or a halogen element. As the monovalentsubstituent are mentioned an alkoxy group, an alkyl group, a carboxylgroup, an acyl group, an aryl group and the like. Among them, the alkoxygroup is preferable in a point that the viscosity of the electrolyte canbe made low. As the halogen element are preferably mentioned fluorine,chlorine, bromine and the like. As the alkoxy group are mentioned, forexample, methoxy group, ethoxy group, methoxyethoxy group, propoxygroup, phenoxy group and the like. Among them, in case of using in thenon-aqueous electrolyte primary battery, methoxy group, ethoxy group,n-propoxy group, phenoxy group are particularly preferable, and in caseof using in the non-aqueous electrolyte secondary battery, methoxygroup, ethoxy group, methoxyethoxy group and phenoxy group areparticularly preferable. In these monovalent substituents, hydrogenelement is preferable to be substituted with a halogen element. As sucha halogen element are preferably mentioned fluorine, chlorine, bromineand the like. As a substituent substituted with fluorine is mentioned,for example, trifluoroethoxy group.

By properly selecting R¹-R⁴, R¹⁰-R¹⁴, Y¹-Y³, Y¹⁰-Y¹⁴ and Z¹ in theformulae (I), (II) and (VIII)-(X), it is possible to synthesizephosphazene derivatives having more preferable viscosity, a solubilitysuitable for adding-mixing and the like. These phosphazene derivativesmay be used alone or in a combination of two or more.

Among the phosphazene derivatives of the formula (II), a phosphazenederivative represented by the following formula (III) is particularlypreferable from a viewpoint that the viscosity of the electrolyte ismade low to improve the low-temperature characteristics of the batteryand further improve the deterioration resistance and safety of theelectrolyte:(NPF₂)_(n)  (III)(wherein n is 3-13).

The phosphazene derivative of the formula (III) is a low viscosityliquid at room temperature (25° C.) and has an action of descending asolidification point. For this end, by adding this phosphazenederivative to the electrolyte, it is possible to give excellentlow-temperature characteristics to the electrolyte, and also thelowering of the electrolyte viscosity is attained, whereby it ispossible to provide a non-aqueous electrolyte battery having a lowinternal resistance and a high electric conductivity. Therefore, it ispossible to provide a non-aqueous electrolyte battery developing anexcellent discharge characteristic over a long time even if it is usedunder low-temperature conditions in a place or season of loweratmosphere temperature.

In the formula (III), n is preferably 3-5, more preferably 3-4,particularly 3 in a point that the excellent low-temperaturecharacteristics can be given to the electrolyte and the viscosity of theelectrolyte can be made low. When the value of n is small, the boilingpoint is low and the property of preventing the fire catch in theapproaching to flame can be improved. While, as the value of n becomeslarge, the boiling point becomes high and it can be stably used even ata high temperature. In order to obtain the target performances byutilizing the above property, it is possible to properly select and useplural phosphazene derivatives.

By properly selecting the value of n in the formula (III), it ispossible to prepare an electrolyte having a more preferable viscosity, asolubility suitable for the mixing and low-temperature characteristics.These phosphazene derivatives may be used alone or in a combination oftwo or more.

The viscosity of the phosphazene derivative represented by the formula(III) is not particularly limited unless it is not more than 20 mPa·s(20 cP), but is preferably not more than 10 mPa·s (10 cP), morepreferably not more than 5 mPa·s (5 cP). Moreover, the viscosity in theinvention is determined by using a viscosity measuring meter (R-typeviscometer Model RE500-SL, made by Toki Sangyo Co., Ltd.) and conductingthe measurement at each revolution rate of 1 rpm, 2 rpm, 3 rpm, 5 rpm, 7rpm, 10 rpm, 20 rpm and 50 rpm for 120 seconds to measure a viscosityunder the revolution rate when an indication value is 50-60% as ananalytical condition.

Among the phosphazene derivatives of the formula (II), from a viewpointof improving the deterioration resistance and safety of the electrolyte,a phosphazene derivative represented by the following formula (IV) isparticularly preferable:(NPR⁵ ₂)_(n)  (IV)(wherein R⁵ is independently a monovalent substituent or a halogenelement, and at least one of all R⁵s is a fluorine-containing monovalentsubstituent or fluorine, provided that all R⁵s are not fluorine, and nis 3-8).

When the phosphazene derivative of the formula (II) is added to theelectrolyte, an excellent self-extinguishing property or a flameretardance can be given to the electrolyte to improve the safety of theelectrolyte. However, when the phosphazene derivative represented by theformula (IV) in which at least one of all R⁵s is a fluorine-containingmonovalent substituent is added to the electrolyte, it is possible togive a more excellent safety to the electrolyte. Further, when thephosphazene derivative represented by the formula (IV) in which at leastone of all R⁵s is fluorine is added to the electrolyte, it is possibleto give a further excellent safety to the electrolyte. That is, thephosphazene derivative represented by the formula (IV) in which at leastone of all R⁵s is a fluorine-containing monovalent substituent orfluorine has an effect of more hardly burning the electrolyte ascompared with the phosphazene derivative containing no fluorine, and cangive a further excellent safety to the electrolyte.

Moreover, a cyclic phosphazene derivative of the formula (IV) in whichall of R⁵s are fluorine and n is 3 is non-combustible and is large inthe effect of preventing fire-catching in the approaching to the flame,but is very low in the boiling point, so that if it is completelyevaporated, the remaining aprotic organic solvent or the like is burntout.

As the monovalent substituent in the formula (IV) are mentioned analkoxy group, an alkyl group, an acyl group, an aryl group, a carboxylgroup and the like, and the alkoxy group is preferable in a point thatthe improvement of the safety of the electrolyte is particularlyexcellent. As the alkoxy group are mentioned methoxy group, ethoxygroup, n-propoxy group, i-propoxy group, butoxy group, and an alkoxygroup-substituted alkoxy group such as methoxyethoxy group or the like.Particularly, methoxy group, ethoxy group and n-propoxy group arepreferable in a point that the improvement of the safety of theelectrolyte is particularly excellent. Also, methoxy group is preferablein a point that the viscosity of the electrolyte is made low.

In the formula (IV), n is preferably 3-5, more preferably 3-4 in a pointthat the excellent safety can be given to the electrolyte.

The above monovalent substituent is preferable to be substituted withfluorine. If all of R⁵s in the formula (IV) is fluorine, at least onemonovalent substituent contains fluorine.

The content of fluorine in the phosphazene derivative is preferably3-70% by weight, more preferably 7-45% by weight. When the content iswithin the above range, the “excellent safety” as an effect inherent tothe invention can be preferably developed.

The molecular structure of the phosphazene derivative represented by theformula (IV) may contain a halogen element such as chlorine, bromine orthe like in addition to fluorine. However, fluorine is most preferable,and chlorine is nest preferable. In the secondary battery, the use offluorine tends to develop the good cycle property as compared with theuse of chlorine.

By properly selecting R⁵ and n in the formula (IV), it is possible toprepare the electrolyte having more preferable safety and viscosity, asolubility suitable for the mixing and the like. The phosphazenederivatives may be used alone or in a combination of two or more.

The viscosity of the phosphazene derivative of the formula (IV) is notparticularly limited unless it is not more than 20 mPa·s (20 cP), but itis preferably not more than 10 mPa·s (10 cP), more preferably 5 mPa·s (5cP) from a viewpoint of the improvement of the electric conductivity andthe improvement of the low-temperature characteristics.

As the phosphazene derivative added to the aprotic organic solvent, froma viewpoint that the deterioration resistance and safety of theelectrolyte are improved while suppressing the rise of the viscosity inthe electrolyte, a phosphazene derivative being solid at 25° C. (roomtemperature) and represented by the following formula (V) is preferable:(NPR⁶ ₂)_(n)  (V)(wherein R⁶ is independently a monovalent substituent or a halogenelement and n is 3-6).

Since the phosphazene derivative of the formula (V) is solid at roomtemperature (25° C.), when it is added to the electrolyte, it isdissolved in the electrolyte to raise the viscosity of the electrolyte.However, when the addition amount is a given value as mentioned later,the rising ratio of the viscosity of the electrolyte becomes low andhence there is provided a non-aqueous electrolyte battery having a lowinternal resistance and a high electric conductivity. In addition, thephosphazene derivative of the formula (V) is soluble in the electrolyte,so that the stability of the electrolyte over a long time is excellent.

In the formula (V), R⁶ is not particularly limited unless it is amonovalent substituent or a halogen element. As the monovalentsubstituent are mentioned an alkoxy group, an alkyl group, a carboxylgroup, an acyl group, an aryl group and the like. As the halogen elementare preferably mentioned halogen elements such as fluorine, chlorine,bromine and the like. Among them, the alkoxy group is preferable in apoint that the rise of the viscosity of the electrolyte can besuppressed. As the alkoxy group are preferable methoxy group, ethoxygroup, methoxyethoxy group, propoxy group (isopropoxy group, n-propoxygroup), phenoxy group, trifluoroethoxy group and the like. Particularly,methoxy group, ethoxy group, propoxy group (isopropoxy group, n-propoxygroup), phenoxy group and trifluoroethoxy group are preferable in apoint that the rise of the viscosity of the electrolyte can besuppressed. The above monovalent substituent is preferable to containthe above halogen element.

In the formula (V), n is particularly preferable to be 3 or 4 in a pointthat the rise of the viscosity of the electrolyte can be suppressed.

As the phosphazene derivative of the formula (V) are particularlypreferable a structure that R⁶ is methoxy group and n is 3 in theformula (V), a structure that R⁶ is at least either methoxy group orphenoxy group and n is 4 in the formula (V), a structure that R⁶ isethoxy group and n is 4 in the formula (V), a structure that R⁶ isisopropoxy group and n is 3 or 4 in the formula (V), a structure that R⁶is n-propoxy group and n is 4 in the formula (V), a structure that R⁶ istrifluoroethoxy group and n is 3 or 4 in the formula (V), and astructure that R⁶ is phenoxy group and n is 3 or 4 in the formula (V) ina point that the rise of the viscosity of the electrolyte can besuppressed.

By properly selecting the substituent and value of n in the formula (V),it is possible to prepare an electrolyte having a more preferableviscosity, a solubility suitable for the mixing and the like. Thesephosphazene derivatives may be used alone or in a combination of two ormore.

The isomer of the phosphazene derivative added to the aprotic organicsolvent is not particularly limited, but from a viewpoint that thelow-temperature characteristics of the electrolyte are improved andfurther the deterioration resistance and safety of the electrolyte areimproved, an isomer represented by the following formula (VI) and of aphosphazene derivative represented by the following formula (VII) ispreferable:

(in the formulae (VI) and (VII), R⁷, R⁸ and R⁹ are independently amonovalent substituent or a halogen element, X² is a substituentcontaining at least one element selected from the group consisting ofcarbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic,antimony, bismuth, oxygen, sulfur, selenium, tellurium and polonium, andY⁷ and Y⁸ are independently a bivalent connecting group, a bivalentelement or a single bond).

When the isomer represented by the formula (VI) and of the phosphazenederivative represented by the formula (VII) is added to the electrolyte,it can develop very excellent low-temperature characteristics in theelectrolyte.

In the formula (VI), R⁷, R⁸ and R⁹ are not particularly limited unlessthey are a monovalent substituent or a halogen element. As themonovalent substituent are mentioned an alkoxy group, an alkyl group, acarboxyl group, an acyl group, an aryl group and the like. As thehalogen element are preferably mentioned halogen elements such asfluorine, chlorine, bromine and the like. Among them, fluorine andalkoxy group are particularly preferable in view of the low-temperaturecharacteristics and electrochemical stability of the electrolyte. Also,fluorine, alkoxy group and alkoxy group containing fluorine or the likeare preferable in a point that the viscosity of the electrolyte is madelow. All of R⁷-R⁹ may be the same kind of the substituent, or some ofthem may be different kinds of the substituent.

As the alkoxy group are mentioned, for example, methoxy group, ethoxygroup, propoxy group, butoxy group, and alkoxy-substituted alkoxy groupsuch as methoxy ethoxy group, methoxyethoxyethoxy group or the like.Among them, all of R⁷-R⁹ are preferable to be methoxy group, ethoxygroup, methoxyethoxy group or methoxyethoxyethoxy group, and all of themare particularly preferable to be methoxy group or ethoxy group from aviewpoint of low viscosity and high dielectric constant. As the alkylgroup are mentioned methyl group, ethyl group, propyl group, butylgroup, pentyl group and the like. As the acyl group are mentioned formylgroup, acetyl group, propionyl group, butyryl group, isobutyryl group,valeryl group and the like. As the aryl group are mentioned phenylgroup, tolyl group, naphthyl group and the like. In these substituents,hydrogen element is preferable to be substituted with a halogen element.As such a halogen element are preferable fluorine, chlorine and bromine,and among them fluorine is most preferable, and chlorine is nextpreferable. In the secondary battery, the use of fluorine tends todevelop the good cycle property as compared with the use of chlorine.

As the bivalent connecting group shown by Y⁷ and Y⁸ in the formula (VI)are mentioned, for example, CH² group and a bivalent connecting groupcontaining at least one element selected from the group consisting ofoxygen, sulfur, selenium, nitrogen, boron, aluminum, scandium, gallium,yttrium, indium, lanthanum, thallium, carbon, silicon, titanium, tin,germanium, zirconium, lead, phosphorus, vanadium, arsenic, niobium,antimony, tantrum, bismuth, chromium, molybdenum, tellurium, polonium,tungsten, iron, cobalt and nickel. Among them, CH₂ group and thebivalent connecting group containing at least one element selected fromthe group consisting of oxygen, sulfur, selenium and nitrogen arepreferable. Also, Y⁷ and Y⁸ may be a bivalent element such as oxygen,sulfur, selenium or the like, or a single bond. The bivalent connectinggroup containing sulfur and/or oxygen, oxygen element and sulfur elementare particularly preferable in a point that the safety of theelectrolyte is improved, and the bivalent connecting group containingoxygen and oxygen element are particularly preferable in a point thatthe low-temperature characteristics of the electrolyte are excellent. Y⁷and Y⁸ may be the same kind or different kinds.

As X² in the formula (VI), from a viewpoint of the consideration on thetoxicity, environment and the like, a substituent containing at leastone element selected from the group consisting of carbon, silicon,nitrogen, phosphorus, oxygen and sulfur is preferable, and a substituenthaving a structure represented by the following formula (XI), (XII) or(XIII) is more preferable.

In the formulae (XI), (XII) and (XIII), R¹⁵-R¹⁹ are independently amonovalent substituent or a halogen element, Y¹⁵-Y¹⁹ are independently abivalent connecting group, a bivalent element or a single bond, and Z²is a bivalent group or a bivalent element.

As R¹⁵-R¹⁹ in the formulae (XI), (XII) and (XIII) are preferablymentioned the same monovalent substituents or halogen elements asdescribed in R⁷-R⁹ of the formula (VI). They may be the same kind in thesame substituent, or some of them may be different kinds. R¹⁵ and R¹⁶ inthe formula (XI), and R¹⁸ and R¹⁹ in the formula (XIII) may be bonded toeach other to form a ring.

As the group shown by Y¹⁵-Y¹⁹ in the formulae (XI), (XII) and (XIII) arementioned the same bivalent connecting groups, bivalent elements or thelike as described in Y⁷-Y⁸ of the formula (VI). Similarly, the bivalentconnecting group containing sulfur and/or oxygen, oxygen element orsulfur element is particularly preferable in a point that the safety ofthe electrolyte is improved. Also, the bivalent connecting groupcontaining oxygen and oxygen element are particularly preferable in apoint that the low-temperature characteristics of the electrolyte areexcellent. They may be the same kind in the same substituent, or some ofthem may be different kinds.

As Z² in the formula (XI) are mentioned, for example, CH₂ group, CHR′group (R′ is an alkyl group, an alkoxyl group, phenyl group or the like,and so forth), NR′ group, and a bivalent group containing at least oneelement selected from the group consisting of oxygen, sulfur, selenium,boron, aluminum, scandium, gallium, yttrium, indium, lanthanum,thallium, carbon, silicon, titanium, tin, germanium, zirconium, lead,phosphorus, vanadium, arsenic, niobium, antimony, tantalum, bismuth,chromium, molybdenum, tellurium, polonium, tungsten, iron, cobalt andnickel. Among them, CH₂ group, CHR′ group, NR′ group and the bivalentgroup containing at least one element selected from the group consistingof oxygen, sulfur and selenium are preferable. Also, Z² may be abivalent element such as oxygen, sulfur, selenium or the like.Particularly, the bivalent group containing sulfur and/or selenium,sulfur element or selenium element is preferable because the safety ofthe electrolyte is improved. Also, the bivalent group containing oxygenand oxygen element are particularly preferable in a point that thelow-temperature characteristics of the electrolyte are excellent.

As to these substituents, in a point that the safety can be effectivelyimproved, the substituent containing phosphorus as shown by the formula(XI) is particularly preferable. Furthermore, when Z², Y¹⁵ and Y¹⁶ inthe formula (XI) are oxygen elements, it is possible to develop veryexcellent low-temperature characteristics in the electrolyte. Also, whenthe substituent is a sulfur-containing substituent as shown by theformula (XII), it is particularly preferable in a point that theinterfacial resistance of the electrolyte is made small.

By properly selecting R⁷-R⁹, R¹⁵-R¹⁹, Y⁷-Y⁸, Y¹⁵-Y¹⁹ and Z² in theformulae (VI) and (XI)-(XIII), it is possible to prepare an electrolytehaving a more preferable viscosity, a solubility suitable for theadding-mixing, and low-temperature characteristics. These compounds maybe used alone or in a combination of two or more.

The isomer of the formula (VI) is an isomer of a phosphazene derivativerepresented by the formula (VII) and can be prepared, for example, byadjusting a vacuum degree and/or a temperature in the formation of thephosphazene derivative represented by the formula (VII). The content ofthe isomer in the electrolyte (volume %) can be measured by thefollowing measuring method.

Measuring Method

It can be measured by finding a peak area of a sample through a gelpermeation chromatography (GPC) or a high-speed liquid chromatography,comparing the found peak area with a previously found area per mole ofthe isomer to obtain a molar ratio, and further converting into a volumewhile considering a specific gravity.

As the phosphazene derivative of the formula (VII) is preferable oneshaving a relatively low viscosity and capable of well dissolving thesupport salt. As R⁷-R⁹, Y⁷-Y⁸ and X² of the formula (VII) are preferablymentioned the same as described in R⁷-R⁹, Y⁷-Y⁸ and X² of the formula(VI).

The phosphazene derivative represented by the formula (I), (II), (V) or(VII), or the isomer of the formula (VI) is preferable to have asubstituent containing a halogen element in its molecular structure.When the molecular structure has the substituent containing the halogenelement, even if the content of the phosphazene derivative or the isomeris small, it is possible to effectively reduce the risk of fire-ignitionin the electrolyte by a halogen gas derived from the substituent.Moreover, the occurrence of a halogen radical may come into problem inthe compound having the halogen element-containing substituent. In caseof phosphazene derivative or the isomer of the phosphazene derivative,this problem is never caused because phosphorus element in the molecularstructure catches the halogen radical to form a stable phosphorushalide.

The content of the halogen element in the phosphazene derivative or theisomer of the phosphazene derivative is preferably 2-80% by weight, morepreferably 2-60% by weight, further preferably 2-50% by weight. When thecontent is less than 2% by weight, the effect by the inclusion of thehalogen element may be not sufficiently developed, while when it exceeds80% by weight, the viscosity becomes higher, and hence when it is addedto the electrolyte, the electric conductivity may lower. As such ahalogen element, fluorine, chlorine, bromine and the like arepreferable, and particularly fluorine is preferable from a viewpoint ofthe provision of good battery characteristics.

The ignition point of the phosphazene derivative represented by theformulae (I), (II), (IV), (V) and (VII) is not particularly limited, butit is preferably not lower than 100° C., more preferably not lower than150° C., further preferably not lower than 300° C. from a viewpoint ofthe fire control and the like. On the other hand, the phosphazenederivative of the formula (III) has no ignition point. The term“ignition point” used herein means concretely means a temperature thatthe flame is widened on a surface of a mass to cover at least 75% of themass surface. The ignition point is a measure observing a tendency offorming a combustible mixture with air. When the phosphazene derivativehas an ignition point above 100° C. or has not an ignition point, thefire or the like is suppressed, and also even if the fire or the like iscaused in the interior of the battery, it is possible to lower the riskthat it is ignited to outblaze on the surface of the electrolyte.

As the phosphazene derivative of the formula (III) or (V), or the isomerof the formula (VI) and the phosphazene derivative of the formula (VII)are added, the decomposition of the support salt is suppressed toconsiderably stabilize the electrolyte. In the conventional electrolytecomprising an ester based organic solvent used in the non-aqueouselectrolyte battery and a support salt as a lithium ion source, thesupport salt is decomposed with the lapse of time and the decomposedmass reacts with a slight amount of water or the like existing in theorganic solvent, whereby there may be caused a case that the electricconduction of the electrolyte lowers or the electrode material isdeteriorated. On the contrary, the phosphazene derivative or the isomerof the phosphazene derivative is added to the conventional electrolyte,the decomposition of the support salt is suppressed and the stability ofthe electrolyte is considerably improved. In genera, LiBF₄, LiPF₆,LiCF₃SO₃, Li(C₃F₅SO₂)₂N, Li(CF₃SO₂)₂N and the like are used as thesupport salt for the non-aqueous electrolyte primary battery.Particularly, LiCF₃SO₃, Li(C₃F₅SO₂)₂N and Li(CF₃SO₂)₂N are preferablebecause the hydrolysis of the support salt itself is low, but LiBF₄ andLiPF₆ can be preferably used owing to the above action of phosphazene.

The contents of the phosphazene derivative and the isomer of thephosphazene derivative in the electrolyte are described below. From aviewpoint of “limit oxygen index”, the content of the phosphazenederivative of the formula (I) or (II) to the electrolyte is preferablynot less than 5 volume %, more preferably 10-50 volume %. By adjustingthe content to the value of the above range is effectively reduced therisk of fire-ignition of the electrolyte. Moreover, the above rangeeffectively reduces the risk of ignition but differs in accordance withthe kind of the support salt and the kind of electrolyte used, so thatit is optimized by properly determining the content so that the systemused is controlled to a lowest viscosity and the limit oxygen index isrendered into not less than 21 volume %.

From a viewpoint of “safety”, the content of the phosphazene derivativeof the formula (III) in the electrolyte is preferably not less than 5volume %, and the content of the phosphazene derivative of the formula(IV) is preferably not less than 10 volume %, more preferably not lessthan 15 volume %, and the content of the phosphazene derivative of theformula (V) is preferably not less than 20 volume %, more preferably notless than 30 volume %, and the total content of the isomer of theformula (VI) and the phosphazene derivative of the formula (VII) ispreferably not less than 20 volume %, more preferably not less than 30volume %. When the content is within the above range, the safety of theelectrolyte can be preferably improved.

From a viewpoint of “low-temperature characteristics”, the content ofthe phosphazene derivative of the formula (III) in the electrolyte ispreferably not less than 1 volume %, more preferably not less than 3volume %, further preferably not less than 5 volume %, and the totalcontent of the isomer of the formula (VI) and the phosphazene derivativeof the formula (VII) not less that 1 volume %, more preferably not lessthan 2 volume %, further preferably not less than 5 volume %. When thecontent is less than 1 volume %, the low-temperature characteristics ofthe electrolyte are not sufficient.

From a viewpoint of “deterioration resistance”, the content of thephosphazene derivative of the formula (III) is preferably not less than2 volume %, more preferably 3-75 volume %, and the content of thephosphazene derivative of the formula (IV) is preferably not less than 2volume %, more preferably 2-75 volume %, and the content of thephosphazene derivative of the formula (V) is preferably not less than 2%by weight, more preferably 2-20% by weight, and the total content of theisomer of the formula (VI) and the phosphazene derivative of the formula(VII) is preferably not less than 2 volume %, more preferably 3-75volume %. When the content is within the above range, the deteriorationof the electrolyte can be preferably suppressed.

From a viewpoint of “lowering of viscosity”, the content of thephosphazene derivative of the formula (III) in the electrolyte ispreferably not less than 3 volume %, more preferably 3-80 volume %. Whenthe content is less than 3 volume %, the viscosity of the electrolytecan not be made sufficiently low.

From a viewpoint of “control of viscosity rise”, the content of thephosphazene derivative of the formula (V) in the electrolyte ispreferably not more than 40% by weight, more preferably not more than35% by weight, further preferably not more than 30% by weight. When thecontent exceeds 40% by weight, the viscosity rise of the electrolytebecomes remarkably large and the internal resistance is high and theelectric conductivity becomes undesirably low.

From a viewpoint of “safety” in the primary battery, a case of includingthe cyclic phosphazene derivative of the formula (IV) or (V), or theisomer of the formula (VI) and the phosphazene derivative of the formula(VII) and LiBF₄ or LiCF₃SO₃, and y-butyrolactone and/or propylenecarbonate is particularly preferable as the electrolyte. In this case,even if the content is small, the safety is very high irrespectively ofthe aforementioned description. That is, the content of the cyclicphosphazene derivative of the formula (IV) in the electrolyte ispreferably not less than 5 volume % in order to develop the excellentsafety. Also, the content of the cyclic phosphazene derivative of theformula (V) in the electrolyte is preferably 5-10% by weight, furtherpreferably more than 10% by weight in case of including LiBF₄ in orderto develop the excellent safety, and preferably 5-25% by weight, furtherpreferably more than 25% by weight in case of including LiCF₃SO₃ inorder to develop the excellent safety. Furthermore, the total content ofthe isomer of the formula (VI) and the phosphazene derivative of theformula (VII) in the electrolyte is preferably 1.5-10 volume %, furtherpreferably more than 10 volume % in case of including LiBF₄ in order todevelop the excellent safety, and preferably 2.5-15 volume %, furtherpreferably more than 15 volume % in case of including LiCF₃SO₃ in orderto develop the excellent safety. Moreover, if it is intended to use at ahigh temperature, a case of including Li(C₂F₅SO₂)₂N, Li(CF₃SO₂)₂N andLiBF₄ as a support salt is also preferable.

On the other hand, from a viewpoint of “safety” in the secondarybattery, a case of including the cyclic phosphazene derivative of theformula (IV) or (V) or the isomer of the formula (VI) and thephosphazene derivative of the formula (VII) and LiPF₆ and ethylenecarbonate and/or propylene carbonate, or a case of including the cyclicphosphazene derivative of the formula (IV) or (V) or the isomer of theformula (VI) and the phosphazene derivative of the formula (VII) andLiCF₃SO₃ and propylene carbonate is particularly preferable as theelectrolyte. In this case, even if the content is small, the safety isvery high irrespectively of the aforementioned description. That is, thecontent of the cyclic phosphazene derivative of the formula (IV) in theelectrolyte is preferably not less than 5 volume % in order to developthe excellent safety. Also, the content of the cyclic phosphazenederivative of the formula (V) in the electrolyte is preferably 2-5% byweight, further preferably more than 5% by weight in order to developthe excellent safety. Furthermore, the total content of the isomer ofthe formula (VI) and the phosphazene derivative of the formula (VII) inthe electrolyte is preferably 1.5-2.5 volume %, further preferably morethan 2.5 volume % in order to develop the excellent safety.

Other Members

As the other member used in the non-aqueous electrolyte batteryaccording to the invention is mentioned a separator interposed betweenpositive and negative electrodes in the non-aqueous electrolyte batteryfor preventing the short-circuiting of current due to the contact ofboth electrodes. As a material of the separator are preferably mentionedmaterials capable of surely preventing the contact of both electrodesand passing or impregnating the electrolyte, for example, non-wovenfabric, thin-layer film and the like of a synthetic resin such aspolytetrafluoroethylene, polypropylene, polyethylene, cellulose-basedresin, polybutylene terephthalate, polyethylene terephthalate or thelike. Among them, microporous film of polypropylene or polyethylenehaving a thickness of about 20-50 μm and a film of cellulose-basedresin, polybutylene terephthalate, polyethylene terephthalate or thelike are particularly preferable.

In the invention, well-known members usually used in the battery can bepreferably used in addition to the separator.

Form of Non-Aqueous Electrolyte Battery

The form of the aforementioned non-aqueous electrolyte battery accordingto the invention is not particularly limited, and preferably includesvarious known forms such as coin type, button type, paper type,cylindrical cells of rectangular or spiral structure and the like. Incase of button type, a non-aqueous electrolyte battery can be preparedby providing sheet-shaped positive electrode and negative electrode, andsandwiching a separator between the positive and negative electrodes andthe like. In case of spiral structure, a non-aqueous electrolyte batterycan be prepared by providing sheet-shaped positive electrodes,sandwiching a collector therebetween, piling a negative electrode(sheet-shaped) thereon and winding them and the like.

The following examples are given in illustration of the invention andare not intended as limitations thereof.

Non-Aqueous Electrolyte Primary Battery

A positive electrode for a lithium primary battery is prepared by thefollowing method. At first, 10 g of an aqueous solution of 3% by mass ofcalcium hydroxide is added to 10 g of manganese dioxide (EMD, made byMitsui Mining Co., Ltd.) while cooling with ice, which are mixed withstirring to prepare a mixed solution. Then, the temperature of the mixedsolution is raised to 50° C. at a rate of 5° C./min to reduce a watercontent in the mixed solution. Subsequently, the temperature of themixed solution is raised to 80° C. at a rate of 10° C./min tosubstantially remove the water content in the mixed solution to obtain amixture of manganese dioxide and calcium hydroxide. Next, thetemperature of this mixture is raised to 300° C. and held at thistemperature for about 3 hours to convert calcium hydroxide into calciumoxide, and thereafter dropped to room temperature by air cooling toobtain powder for positive electrode dispersing calcium oxide betweenparticles of manganese dioxide. Moreover, the mass of calcium oxide inthe powder for positive electrode is 2.3% per the mass of manganesedioxide.

The powder for positive electrode is mixed and kneaded with acetyleneblack and polytetrafluoroethylene (PTFE) at a ratio of 8:1:1 (by mass)and the resulting kneaded mass is applied through a doctor blade anddried by hot air (100-120° C.) and punched out by a punching machine of16 mmφ to prepare a positive electrode for a lithium primary battery.Moreover, the mass of the positive electrode is 20 mg.

This positive electrode is used to prepare a lithium primary battery asfollows. Moreover, a lithium foil punched out into 16 mmφ (thickness:0.5 mm) is used in a negative electrode, and a nickel foil is used in acollector. Also, an electrolyte is prepared by dissolving LiBF₄ inγ-butyrolactone (GBL) at a concentration of 0.75 mol/L. As a separatoris used a cellulose separator (TF4030, made by Nippon Kodo Kami KogyoCo., Ltd.), through which the positive and negative electrodes areopposed to each other, and the electrolyte is poured and sealed toprepare a lithium primary battery of CR2016 type.

As the battery is discharged to 1.5 V (lower limit voltage) at aconstant current of 1 mA (0.2 C) in ambient atmosphere of 25° C., adischarge capacity at room temperature is measured to be 275 mAh/g.

Also, a battery prepared in the same manner as mentioned above is storedat 120° C. for 60 hours and then a discharge capacity at roomtemperature after the storing is measured under the same conditions asmentioned above to be 200 mAh/g.

Further, a limit oxygen index of the above electrolyte is 19.1 volume %as measured according to JIS K7201.

CONVENTIONAL EXAMPLE 1

A lithium primary battery is prepared by mixing and kneading manganesedioxide (EMD, made by Mitsui Mining Co., Ltd.) with acetylene black andpolytetrafluoroethylene (PTFE) at a ratio of 8:1:1 (by mass) in the samemanner as in Example 1 except that calcium oxide in not dispersedbetween the particles of manganese dioxide, and then the dischargecapacity is measured in the same manner as mentioned above. As a result,the discharge capacity at room temperature just after the preparation is250 mAh/g, and the discharge capacity at room temperature after thestoring at 120° C. for 60 hours is 151 mAh/g.

EXAMPLES 2-3 AND COMPARATIVE EXAMPLES 1-2

A powder for positive electrode is prepared in the same manner as inExample 1 except that an amount of calcium oxide dispersing between theparticles of manganese dioxide is changed as shown in Table 1, and thena lithium primary battery is prepared. With respect to the thus obtainedlithium primary batteries, the discharge capacity is measured in thesame manner as in Example 1. The results are shown in Table 1. TABLE 1Comparative Comparative unit Example 1 Example 2 Example 3 Example 1Example 2 Amount of % by mass 2.3 0.5 4 0.3 5 calcium oxide DischargemAh/g 275 278 277 253 255 capacity just after preparation DischargemAh/g 200 205 213 170 185 capacity after the storing at high temperature*1*1: storing at 120° C. for 60 hours

EXAMPLES 4-5

A powder for positive electrode is prepared in the same manner as inExample 1 except that magnesium oxide or barium oxide is dispersedbetween the particles of manganese dioxide instead of calcium oxide(mass of each alkaline earth metal oxide per mass of manganese dioxideis 2.3%), and then a lithium primary battery is prepared. With respectto the thus obtained lithium primary batteries, the discharge capacityis measured in the same manner as in Example 1. The results are shown inTable 2. TABLE 2 Example 1 Example 4 Example 5 Kind of alkaline earthmetal oxide CaO MgO BaO Discharge capacity just after 275 272 271preparation (mAh/g) Discharge capacity after the storing 200 195 199 athigh temperature (mAh/g)*1*1storing at 120° C. for 60 hours

EXAMPLE 6

A lithium primary battery is prepared in the same manner as in Example 1except that the electrolyte is prepared by dissolving LiBF₄ (lithiumsalt) at a concentration of 0.75 mol/L (M) in a mixed solution of 10volume % of a phosphazene derivative A (a cyclic phosphazene derivativecompound of the formula (IV) in which n is 3 and two of six R⁵s areethoxy group and remaining four thereof are fluorine, viscosity at 25°C.: 1.2 mPa·s (1.2 cP)) and 90 volume % of y-butyrolactone (GBL), andthen the discharge capacity is measured in the same manner as mentionedabove. As a result, the discharge capacity just after the preparation is280 mAh/g, and the discharge capacity after the storing at 120° C. for60 hours is 220 mAh/g. Also, the limit oxygen index of the electrolyteis 24.2 volume % as measured in the same manner as in Example 1.

EXAMPLE 7

An electrolyte is prepared in the same manner as in Example 6 exceptthat a phosphazene derivative B (a cyclic phosphazene derivativecompound of the formula (IV) in which n is 3 and one of six R⁵s isethoxy group and remaining five thereof are fluorine, viscosity at 25°C.: 1.2 mPa·s (1.2 cP)) is used instead of the phosphazene derivative A,and a lithium primary battery is prepared, and then the dischargecapacity and the limit oxygen index are measured in the same manner asmentioned above. The results are shown in Table 3.

EXAMPLE 8

An electrolyte is prepared in the same manner as in Example 6 exceptthat a phosphazene derivative C (a cyclic phosphazene derivativecompound of the formula (IV) in which n is 4 and one of eight R⁵s isethoxy group and remaining seven thereof are fluorine, viscosity at 25°C.: 1.3 mPa·s (1.3 cP)) is used instead of the phosphazene derivative A,and a lithium primary battery is prepared, and then the dischargecapacity and the limit oxygen index are measured in the same manner asmentioned above. The results are shown in Table 3.

EXAMPLE 9

An electrolyte is prepared in the same manner as in Example 6 exceptthat a phosphazene derivative D (a cyclic phosphazene derivativecompound of the formula (IV) in which n is 3 and one of six R⁵s isOCH₂CF₃ and remaining five thereof are fluorine, viscosity at 25° C.:1.8 mPa·s (1.8 cP)) is used instead of the phosphazene derivative A, anda lithium primary battery is prepared, and then the discharge capacityand the limit oxygen index are measured in the same manner as mentionedabove. The results are shown in Table 3. TABLE 3 Example 1 Example 6Example 7 Example 8 Example 9 Kind of — phosphazene A phosphazene Bphosphazene C phosphazene D phosphazene Discharge 275 280 280 280 277capacity just after preparation (mAh/g) Discharge 200 220 203 209 230capacity after the storing at high temperature (mAh/g) *1 Limit oxygen19.1 23.7 24.2 25.1 23.9 index (volume %)*1: storing at 120° C. for 60 hours

As seen from these results, the discharge capacity at room temperaturejust after the preparation and the discharge capacity at roomtemperature after the storing at the high temperature are improved bydispersing the alkaline earth metal oxide between the particles ofmanganese dioxide. Also, it has been found that the discharge capacityat room temperature just after the preparation and the dischargecapacity at room temperature after the storing at the high temperatureare further improved and the limit oxygen index of the electrolyte israised to improve the safety of the battery by adding the phosphazenederivative to prepare the electrolyte in addition to the dispersion ofthe alkaline earth metal oxide between the particles of manganesedioxide.

Non-Aqueous Electrolyte Secondary Battery

EXAMPLE 10

A positive electrode for a non-aqueous electrolyte secondary battery isprepared by the following method. At first, 10 g of an aqueous solutionof 3% by mass of calcium hydroxide is added to 10 g of LiCoO₂ (made byNihon Kagaku Kogyo Co., Ltd.) while cooling with ice, which are mixedwith stirring to prepare a mixed solution. Then, the temperature of themixed solution is raised to 50° C. at a rate of 5° C./min to reduce awater content in the mixed solution. Subsequently, the temperature ofthe mixed solution is raised to 80° C. at a rate of 10° C./min tosubstantially remove the water content in the mixed solution to obtain amixture of LiCoO₂ and calcium hydroxide. Next, the temperature of thismixture is raised to 300° C. and held at this temperature for about 3hours to convert calcium hydroxide into calcium oxide, and thereafterdropped to room temperature by air cooling to obtain powder for positiveelectrode dispersing calcium oxide between particles of LiCoO₂.Moreover, the mass of calcium oxide in the powder for positive electrodeis 2.3% per the mass of LiCoO₂.

To 100 parts by mass of the powder for positive electrode are added 10parts by mass of acetylene black and 10 parts by mass ofpolytetrafluoroeythylene (PTFE) and kneaded with an organic solvent(mixed solvent of 50/50 volume % of ethyl acetate and ethanol), which issubjected to a rolling through rollers to prepare a thin-layeredpositive electrode sheet having a thickness of 100 μm and a width of 40mm. Thereafter, the two positive electrode sheets are used, and analuminum foil of 25 μm in thickness (collector) coated on its surfacewith an electrically conductive adhesive is interposed therebetween, anda lithium metal foil of 150 μm in thickness is piled thereon through aseparator of 25 μm in thickness (microporous film made ofpolypropylene), which are wound up to prepare a cylinder type battery.The length of the positive electrode in the cylinder type battery isabout 260 mm.

An electrolyte is prepared by dissolving LiBF4 (support salt) at aconcentration of 1 mol/kg in a mixed solution of 50 volume % of diethylcarbonate and 50 volume % of ethylene carbonate. The electrolyte ispoured in the cylinder type battery and sealed to prepare a size AAlithium battery.

This battery is subjected to recharging-discharging of 50 cycles in anambient atmosphere of 25° C. under conditions of upper limit voltage:4.5 V, lower limit voltage: 3.0 V, discharge current: 100 mA andrecharge current: 50 mA. As a result, the recharge-discharge capacity atinitial stage is 145 mAh/g, and the recharge-discharge capacity after 50cycles is 143 mAh/g.

Also, a battery prepared in the same manner as mentioned above is storedat 70° C. for 60 hours, and the recharge-discharge capacity after thestoring is measured in the same manner as mentioned above. As a result,the recharge-discharge capacity at initial stage is 142 mAh/g, and therecharge-discharge capacity after 50 cycles is 140 mAh/g.

Furthermore, the limit oxygen index of the electrolyte is 17.1 volume %as measured according to JIS K7201.

CONVENTIONAL EXAMPLE 2

A size AA lithium battery is prepared in the same manner as in Example10 except that a thin-layered positive electrode sheet is prepared byadding 10 parts by mass of acetylene black and 10 parts by mass ofpolytetrafluoroethylene (PTFE) to 100 parts by mass of LiCoO₂, kneadingwith an organic solvent (mixed solvent of 50/50 volume % of ethylacetate and ethanol) and subjecting to a rolling through rollers, andthen the recharge-discharge capacity is measured in the same manner asmentioned above. As a result, the initial recharge-discharge capacityjust after the preparation is 141 mAh/g and the recharge-dischargecapacity after 50 cycles is 130 mAh/g. Also, the initialrecharge-discharge capacity after the storing at 70° C. for 60 hours is133 mAh/g and the recharge-discharge capacity after 50 cycles is 116mAh/g.

EXAMPLES 11-12 AND COMPARATIVE EXAMPLES 3-4

A lithium secondary battery is prepared by preparing powder for positiveelectrode in the same manner as in Example 10 except that an amount ofcalcium oxide dispersing between particles of LiCoO₂ is changed as shownin Table 4. With respect to the thus obtained batteries, therecharge-discharge capacity is measured in the same manner as in Example10. The results are shown in Table 4. TABLE 4 Example Example ExampleComparative Comparative 10 11 12 Example 3 Example 4 Amount of calciumoxide 2.3 0.5 4 0.3 5 (% by mass) Just after Initial recharge- 145 145144 144 141 preparation discharge capacity (mAh/g) Recharge- 143 144 143142 132 discharge capacity after 50 cycles (mAh/g) After storing Initialrecharge- 142 142 142 133 140 at high discharge capacity temperature *2(mAh/g) Recharge- 140 141 142 110 130 discharge capacity after 50 cycles(mAh/g)*2: storing at 70° C. for 60 hours

EXAMPLE 13

A lithium secondary battery is prepared by preparing powder for positiveelectrode in the same manner as in Example 10 except that LiMn₂O₄ (TypeE09Z, made by Nikki Kagaku Co., Ltd.) is used instead of LiCoO₂ as anactive substance for positive electrode. With respect to the thusobtained battery, the recharge-discharge capacity is measured in thesame manner as in Example 10. The results are shown in Table 5.

EXAMPLES 14-15 AND COMPARATIVE EXAMPLES 5-6

A lithium secondary battery is prepared by preparing powder for positiveelectrode in the same manner as in Example 10 except that an amount ofcalcium oxide dispersing between particles of LiMn₂O₄ is changed asshown in Table 4. With respect to the thus obtained batteries, therecharge-discharge capacity is measured in the same manner as in Example10. The results are shown in Table 5. TABLE 5 Example Example ExampleComparative Comparative 13 14 15 Example 5 Example 6 Amount of calciumoxide 2.3 0.5 4 0.3 5 (% by mass) Just after Initial recharge- 104 104104 104 98 preparation discharge capacity (mAh/g) Recharge- 102 103 103103 77 discharge capacity after 50 cycles (mAh/g) After storing Initialrecharge- 100 101 101 101 94 at high discharge capacity temperature *2(mAh/g) Recharge- 94 95 94 95 59 discharge capacity after 50 cycles(mAh/g)*2: storing at 70° C. for 60 hours

EXAMPLE 16

To an aqueous solution of nickel nitrate (Ni(NO₃)₂) is added an aqueoussolution of 1 M (mol/L) of ammonia (NH₃) to precipitate nickel hydroxidethrough a sol-gel method. After the filtration, the precipitates aredried at 80° C. in air for 12 hours. Thereafter, it is added andsufficiently mixed with lithium hydroxide (LiOH) and fired at 950° C. inan oxygen atmosphere for 12 hours to prepare LiNiO₂.

A lithium secondary battery is prepared by preparing powder for positiveelectrode in the same manner as in Example 10 except that the aboveprepared LiNiO₂ is used instead of LiCoO₂ as an active substance forpositive electrode. With respect to the thus obtained battery, therecharge-discharge capacity is measured in the same manner as in Example10. The results are shown in Table 6.

EXAMPLES 17-18 AND COMPARATIVE EXAMPLES 7-8

A lithium secondary battery is prepared by preparing powder for positiveelectrode in the same manner as in Example 10 except that an amount ofcalcium oxide dispersing between particles of LiNiO₂ is changed as shownin Table 6. With respect to the thus obtained batteries, therecharge-discharge capacity is measured in the same manner as in Example10. The results are shown in Table 6. TABLE 6 Example Example ExampleComparative Comparative 16 17 18 Example 7 Example 8 Amount of calciumoxide 2.3 0.5 4 0.3 5 (% by mass) Just after Initial recharge- 158 158158 158 158 preparation discharge capacity (mAh/g) Recharge- 156 156 155156 142 discharge capacity after 50 cycles (mAh/g) After storing Initialrecharge- 153 154 152 154 150 at high discharge capacity temperature *2(mAh/g) Recharge- 150 150 150 151 122 discharge capacity after 50 cycles(mAh/g)*2: storing at 70° C. for 60 hours

EXAMPLES 19-20

A powder for positive electrode is prepared in the same manner as inExample 10 except that magnesium oxide or barium oxide is dispersedbetween the particles of LiCoO₂ instead of calcium oxide (mass of eachalkaline earth metal oxide per mass of LiCoO₂ is 2.3%), and then alithium secondary battery is prepared. With respect to the thus obtainedbatteries, the recharge-discharge capacity is measured in the samemanner as in Example 10. The results are shown in Table 7. TABLE 7Example 10 Example 11 Example 12 Kind of alkaline earth metal oxide CaOMgO BaO Just after Initial recharge- 145 144 145 preparation dischargecapacity (mAh/g) Recharge-discharge capacity 143 142 140 after 50 cycles(mAh/g) After storing Initial recharge- 142 141 140 at high dischargecapacity (mAh/g) temperature*2 Recharge-discharge capacity 140 140 139after 50 cycles (mAh/g)*2storing at 70° C. for 60 hours

EXAMPLES 21-22

A powder for positive electrode is prepared in the same manner as inExample 13 except that magnesium oxide or barium oxide is dispersedbetween the particles of LiMn₂O₄ instead of calcium oxide (mass of eachalkaline earth metal oxide per mass of LiMn₂O₄ is 2.3%), and then alithium secondary battery is prepared. With respect to the thus obtainedbatteries, the recharge-discharge capacity is measured in the samemanner as in Example 10. The results are shown in Table 8. TABLE 8Example 13 Example 21 Example 22 Kind of alkaline earth metal oxide CaOMgO BaO Just after Initial recharge- 104 103 102 preparation dischargecapacity (mAh/g) Recharge-discharge capacity 102 101 99 after 50 cycles(mAh/g) After storing Initial recharge- 100 100 98 at high dischargecapacity (mAh/g) temperature*2 Recharge-discharge capacity 94 95 94after 50 cycles (mAh/g)*2storing at 70° C. for 60 hours

EXAMPLES 23-24

A powder for positive electrode is prepared in the same manner as inExample 16 except that magnesium oxide or barium oxide is dispersedbetween the particles of LiNiO₂ instead of calcium oxide (mass of eachalkaline earth metal oxide per mass of LiNiO₂ is 2.3%), and then alithium secondary battery is prepared. With respect to the thus obtainedbatteries, the recharge-discharge capacity is measured in the samemanner as in Example 10. The results are shown in Table 9. TABLE 9Example 16 Example 23 Example 24 Kind of alkaline earth metal oxide CaOMgO BaO Just after Initial recharge- 158 154 154 preparation dischargecapacity (mAh/g) Recharge-discharge capacity 156 150 151 after 50 cycles(mAh/g) After storing Initial recharge- 153 150 150 at high dischargecapacity (mAh/g) temperature*2 Recharge-discharge capacity 150 148 147after 50 cycles (mAh/g)*2storing at 70° C. for 60 hours

EXAMPLE 25

A size AA lithium secondary battery is prepared in the same manner as inExample 10 except that an electrolyte is prepared by dissolving LiBF₄(lithium salt) at a concentration of 1 mol/kg in a mixed solution of 10volume % of a phosphazene derivative A (a cyclic phosphazene derivativeof the formula (IV) in which n is 3 and two of six R⁵s are ethoxy groupand the remaining four thereof are fluorine, viscosity at 25° C.: 1.2mPa·s (1.2 cP)), 45 volume % of diethyl carbonate and 45 volume % ofethylene carbonate, and then the recharge-discharge capacity is measuredin the same manner as described above. As a result, therecharge-discharge capacity just after the preparation is 146 mAh/g, andthe recharge-discharge capacity after 50 cycles is 144 mAh/g. Also, theinitial recharge-discharge capacity after the storing at 70° C. for 60hours is 142 mAh/g, and the recharge-discharge capacity after 50 cyclesis 140 mAh/g. On the other hand, the limit oxygen index of theelectrolyte is 22.9 volume % as measured in the same manner as inExample 10.

EXAMPLE 26

An electrolyte is prepared in the same manner as in Example 25 exceptthat a phosphazene derivative B (a cyclic phosphazene derivativecompound of the formula (IV) in which n is 3 and one of six R⁵s isethoxy group and remaining five thereof are fluorine, viscosity at 25°C.: 1.2 mPa·s (1.2 cP)) is used instead of the phosphazene derivative A,and a non-aqueous electrolyte secondary battery is prepared, and thenthe recharge-discharge capacity and the limit oxygen index are measuredin the same manner as mentioned above. The results are shown in Table10.

EXAMPLE 27

An electrolyte is prepared in the same manner as in Example 25 exceptthat a phosphazene derivative C (a cyclic phosphazene derivativecompound of the formula (IV) in which n is 4 and one of eight R⁵s isethoxy group and remaining seven thereof are fluorine, viscosity at 25°C.: 1.3 mPa·s (1.3 cP)) is used instead of the phosphazene derivative A,and a non-aqueous electrolyte secondary battery is prepared, and thenthe recharge-discharge capacity and the limit oxygen index are measuredin the same manner as mentioned above. The results are shown in Table10.

EXAMPLE 28

An electrolyte is prepared in the same manner as in Example 25 exceptthat a phosphazene derivative D (a cyclic phosphazene derivativecompound of the formula (IV) in which n is 3 and one of six R⁵s isOCH₂CF₃ and remaining five thereof are fluorine, viscosity at 25° C.:1.8 mPa·s (1.8 cP)) is used instead of the phosphazene derivative A, anda non-aqueous electrolyte secondary battery is prepared, and then therecharge-discharge capacity and the limit oxygen index are measured inthe same manner as mentioned above. The results are shown in Table 10.TABLE 10 Example 10 Example 25 Example 26 Example 27 Example 28 Kind ofphosphazene — phosphazene A phosphazene B phosphazene C phosphazene DJust after Initial recharge- 145 146 147 147 145 preparation dischargecapacity (mAh/g) Recharge- 143 144 144 145 142 discharge capacity after50 cycles (mAh/g) After storing Initial recharge- 142 142 142 144 144 athigh discharge capacity temperature *2 (mAh/g) Recharge- 140 140 139 141142 discharge capacity after 50 cycles (mAh/g) Limit oxygen index(volume %) 17.1 22.9 23.8 24.3 23.9*2: storing at 70° C. for 60 hours

As seen from these results, the recharge-discharge capacities and cycleproperties just after the preparation and after the storing at the hightemperature are improved by dispersing the alkaline earth metal oxidebetween the particles of the lithium-containing composite oxide. Also,it has been found that the recharge-discharge capacities and cycleproperties just after the preparation and after the storing at the hightemperature are further improved and the limit oxygen index of theelectrolyte is raised to improve the safety of the battery by adding thephosphazene derivative to prepare the electrolyte in addition to thedispersion of the alkaline earth metal oxide between the particles ofthe lithium-containing composite oxide. Moreover, similar results areobtained even when each of LiNiO₂ and LiMn₂O₄ is used instead of LiCoO₂as an active substance for positive electrode.

INDUSTRIAL APPLICABILITY

According to the invention, there can be provided a non-aqueouselectrolyte primary battery having a high discharge capacity andexcellent high-temperature characteristics by using a positive electrodemade from powder obtained by dispersing an alkaline earth metal oxidebetween particles of manganese dioxide to constitute the non-aqueouselectrolyte primary battery. Also, there can be provided a non-aqueouselectrolyte primary battery having a considerably high dischargecapacity and more excellent high-temperature characteristics and furthera high safety by using a positive electrode made from powder obtained bydispersing an alkaline earth metal oxide between particles of manganesedioxide and an electrolyte added with a phosphazene derivative and/or anisomer of a phosphazene derivative to constitute the non-aqueouselectrolyte primary battery.

Also, according to the invention, there can be provided a non-aqueouselectrolyte secondary battery having a high recharge-discharge capacityand excellent high-temperature characteristics by using a positiveelectrode made from powder obtained by dispersing an alkaline earthmetal oxide between particles of lithium-containing composite oxide toconstitute the non-aqueous electrolyte secondary battery. Furthermore,there can be provided a non-aqueous electrolyte secondary battery havinga considerably high recharge-discharge capacity and more excellenthigh-temperature characteristics and further a high safety by using apositive electrode made from powder obtained by dispersing an alkalineearth metal oxide between particles of lithium-containing compositeoxide and an electrolyte added with a phosphazene derivative and/or anisomer of a phosphazene derivative to constitute the non-aqueouselectrolyte secondary battery.

1. A non-aqueous electrolyte primary battery characterized by dispersingat least one alkaline earth metal oxide selected from the groupconsisting of magnesium oxide, calcium oxide and barium oxide betweenparticles of manganese dioxide.
 2. A non-aqueous electrolyte primarybattery according to claim 1, wherein the alkaline earth metal oxide iscalcium oxide.
 3. A non-aqueous electrolyte primary battery according toclaim 1, wherein a mass of the alkaline earth metal oxide is 0.5-4%based on a mass of manganese dioxide.
 4. A non-aqueous electrolyteprimary battery according to claim 1, wherein the alkaline earth metaloxide has a particle size of 10-80 nm.
 5. A method of producing apositive electrode for a non-aqueous electrolyte primary battery, whichcomprises the steps of: (I) a step of adding an aqueous solution of atleast one alkaline earth metal hydroxide selected from the groupconsisting of an aqueous solution of magnesium hydroxide, an aqueoussolution of calcium hydroxide and an aqueous solution of bariumhydroxide to manganese dioxide while cooling below 15° C. and thenmixing them with stirring to prepare a mixed solution; (II) a step ofraising a temperature of the mixed solution to 45-55° C. at a rate of1-10° C./min to reduce a water content of the mixed solution and furtherto 65-85° C. at a rate of 10-15° C./min to remove the water content ofthe mixed solution to thereby form a mixture of manganese dioxide andalkaline earth metal hydroxide; (III) a step of raising a temperature ofthe mixture to 290-310° C. and holding at this temperature for a giventime to convert the alkaline earth metal hydroxide into an alkalineearth metal oxide to thereby prepare powder for a positive electrodedispersing the alkaline earth metal oxide between particles of manganesedioxide; and (IV) a step of shaping the powder for a positive electrodeto produce a positive electrode.
 6. A method of producing a positiveelectrode for a non-aqueous electrolyte primary battery according toclaim 5, wherein the aqueous solution of the alkaline earth metalhydroxide is an aqueous solution of calcium hydroxide.
 7. A non-aqueouselectrolyte primary battery comprising a positive electrode as claimedin claim 1, a negative electrode, and an electrolyte comprising anaprotic organic solvent and a support salt.
 8. A non-aqueous electrolyteprimary battery according to claim 7, wherein the aprotic organicsolvent is added with a phosphazene derivative and/or an isomer of aphosphazene derivative.
 9. A non-aqueous electrolyte primary batteryaccording to claim 8, wherein the phosphazene derivative has a viscosityat 25° C. of not more than 300 mPa·s (300 cP) and is represented by thefollowing formula (I) or (II):

(wherein R¹, R² and R³ are independently a monovalent substituent or ahalogen element, X¹ is a substituent containing at least one elementselected from the group consisting of carbon, silicon, germanium, tin,nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur,selenium, tellurium and polonium, and Y¹, Y² and Y³ are independently abivalent connecting group, a bivalent element or a single bond), or(NPR⁴ ₂)_(n)  (II) (wherein R⁴ is a monovalent substituent or a halogenelement, and n is 3-15).
 10. A non-aqueous electrolyte primary batteryaccording to claim 9, wherein the phosphazene derivative of the formula(II) is represented by the following formula (III):(NPF₂)_(n)  (III) (wherein n is 3-13).
 11. A non-aqueous electrolyteprimary battery according to claim 9, wherein the phosphazene derivativeof the formula (II) is represented by the following formula (IV):(NPR⁵ ₂)_(n)  (IV) (wherein R⁵ is a monovalent substituent or a halogenelement, and at least one of all R⁵s is a fluorine-containing monovalentsubstituent or fluorine, provided that all R⁵s are not fluorine, and nis 3-8).
 12. A non-aqueous electrolyte primary battery according toclaim 8, wherein the phosphazene derivative is a solid at 25° C. and isrepresented by the following formula (V):(NPR⁶ ₂)_(n)  (V) (wherein R⁶ is a monovalent substituent or a halogenelement, and n is 3-6).
 13. A non-aqueous electrolyte primary batteryaccording to claim 8, wherein the isomer of the phosphazene derivativeis represented by the following formula (VI) and is an isomer of aphosphazene derivative represented by the following formula (VII):

(in the formulae (VI) and (VII), R⁷, R⁸ and R⁹ are independently amonovalent substituent or a halogen element, X² is a substituentcontaining at least one element selected from the group consisting ofcarbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic,antimony, bismuth, oxygen, sulfur, selenium, tellurium and polonium, andY⁷ and Y⁸ are independently a bivalent connecting group, a bivalentelement or a single bond).
 14. A non-aqueous electrolyte secondarybattery characterized by dispersing at least one alkaline earth metaloxide selected from the group consisting of magnesium oxide, calciumoxide and barium oxide between particles of at least onelithium-containing composite oxide selected from the group consisting ofLiCoO₂, LiNiO₂ and LiMn₂O₄.
 15. A non-aqueous electrolyte secondarybattery according to claim 14, wherein the alkaline earth metal oxide iscalcium oxide.
 16. A non-aqueous electrolyte secondary battery accordingto claim 14, wherein a mass of the alkaline earth metal oxide is 0.5-4%based on a mass of the lithium-containing composite oxide.
 17. Anon-aqueous electrolyte secondary battery according to claim 14, whereinthe alkaline earth metal oxide has a particle size of 10-80 nm.
 18. Amethod of producing a positive electrode for a non-aqueous electrolytesecondary battery, which comprises the steps of: (I) a step of adding anaqueous solution of at least one alkaline earth metal hydroxide selectedfrom the group consisting of an aqueous solution of magnesium hydroxide,an aqueous solution of calcium hydroxide and an aqueous solution ofbarium hydroxide to at least one lithium-containing composite oxideselected from the group consisting of LiCoO₂, LiNiO₂ and LiMn₂O₄ whilecooling below 15° C. and then mixing them with stirring to prepare amixed solution; (II) a step of raising a temperature of the mixedsolution to 45-55° C. at a rate of 1-10° C./min to reduce a watercontent of the mixed solution and further to 65-85° C. at a rate of10-15° C./min to remove the water content of the mixed solution tothereby form a mixture of lithium-containing composite oxide andalkaline earth metal hydroxide; (III) a step of raising a temperature ofthe mixture to 290-310° C. and holding at this temperature for a giventime to convert the alkaline earth metal hydroxide into an alkalineearth metal oxide to thereby prepare powder for a positive electrodedispersing the alkaline earth metal oxide between particles of thelithium-containing composite oxide; and (IV) a step of shaping thepowder for a positive electrode to produce a positive electrode.
 19. Amethod of producing a positive electrode for a non-aqueous electrolytesecondary battery according to claim 18, wherein the aqueous solution ofthe alkaline earth metal hydroxide is an aqueous solution of calciumhydroxide.
 20. A non-aqueous electrolyte secondary battery comprising apositive electrode as claimed in claim 14, a negative electrode, and anelectrolyte comprising an aprotic organic solvent and a support salt.21. A non-aqueous electrolyte secondary battery according to claim 20,wherein the aprotic organic solvent is added with a phosphazenederivative and/or an isomer of a phosphazene derivative.
 22. Anon-aqueous electrolyte secondary battery according to claim 21, whereinthe phosphazene derivative has a viscosity at 25° C. of not more than300 mPa·s (300 cP) and is represented by the following formula (I) or(II):

(wherein R¹, R² and R³ are independently a monovalent substituent or ahalogen element, X¹ is a substituent containing at least one elementselected from the group consisting of carbon, silicon, germanium, tin,nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur,selenium, tellurium and polonium, and Y¹, Y² and Y³ are independently abivalent connecting group, a bivalent element or a single bond), or(NPR⁴ ₂)_(n)  (II) (wherein R⁴ is a monovalent substituent or a halogenelement, and n is 3-15).
 23. A non-aqueous electrolyte secondary batteryaccording to claim 22, wherein the phosphazene derivative of the formula(II) is represented by the following formula (III):(NPF₂)_(n)  (III) (wherein n is 3-13).
 24. A non-aqueous electrolytesecondary battery according to claim 22, wherein the phosphazenederivative of the formula (II) is represented by the following formula(IV):(NPR⁵ ₂)_(n)  (IV) (wherein R⁵ is a monovalent substituent or a halogenelement, and at least one of all R⁵s is a fluorine-containing monovalentsubstituent or fluorine, provided that all R⁵s are not fluorine, and nis 3-8).
 25. A non-aqueous electrolyte secondary battery according toclaim 21, wherein the phosphazene derivative is a solid at 25° C. and isrepresented by the following formula (V):(NPR⁶ ₂)_(n)  (V) (wherein R⁶ is a monovalent substituent or a halogenelement, and n is 3-6).
 26. A non-aqueous electrolyte secondary batteryaccording to claim 21, wherein the isomer of the phosphazene derivativeis represented by the following formula (VI) and is an isomer of aphosphazene derivative represented by the following formula (VII):

(in the formulae (VI) and (VII), R⁷, R⁸ and R⁹ are independently amonovalent substituent or a halogen element, X² is a substituentcontaining at least one element selected from the group consisting ofcarbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic,antimony, bismuth, oxygen, sulfur, selenium, tellurium and polonium, andY⁷ and Y⁸ are independently a bivalent connecting group, a bivalentelement or a single bond).